Regional Brazilian diet-induced pre-natal malnutrition in rats is correlated with the proliferation of cultured vascular smooth muscle cells

OBJECTIVES: Pre-natal malnutrition induces hypertension and insulin resistance, pathologies commonly linked to atherosclerotic disease. The proliferation of vascular smooth muscle cells (SMCs) is important during development of the atherosclerotic plaque. In this work, we investigated whether the serum of pre-natal malnourished Wistar rats could alter the proliferation of aortic and renal artery SMCs in culture. Malnutrition was induced by feeding a basic regional diet available in a rural area of Pernambuco State, Brazil. This diet was rich in carbohydrates and deficient in proteins, lipids, vitamins and minerals, including sodium chloride. METHODS AND RESULTS: Serum was obtained from the blood of 90-day-old control and pre-natal undernourished rats. SMCs from control Wistar rats at the 6th passage were allowed to adhere to plates in Dulbecco's modified Eagle's medium (DMEM) supplemented with fetal calf serum (10%). Subsequently, the SMCs were maintained in DMEM supplemented with rat serum (10%). The number of cells was counted on the 3rd, 6th and 8th days of culture into rat serum. [3H]-thymidine incorporation into SMCs was evaluated after 20 h or 6 days of incubation. The birth weight of male and female undernourished offspring was 25% (p<0.05) and 46% (p<0.05) lower, respectively, than their corresponding control groups. On the 8th day of culture, the number of aortic SMCs in the serum of undernourished male and female rats, as well as renal artery SMCs in the serum of undernourished female rats, was higher than in the serum of control rats. The [3H]-thymidine incorporation was higher in aortic SMCs incubated for 6 days in the serum of undernourished male and female rats. At confluence, the density of aortic SMCs was higher than that of renal artery SMCs. CONCLUSIONS: Pre-natal malnutrition produces serum with altered properties that can affect the proliferation of SMCs and may contribute to atherosclerotic disease.     

Ontogeny of the in vitro growth hormone stimulatory effect of thyrotropin-releasing hormone in the rat

The ontogenic changes in the somatotroph's responsiveness to TRH were examined in enzymatically dissociated rat pituitary cells in primary monolayer culture. Exposure to TRH (10(-8) M) caused a significant increase in GH release in cultured pituitary cells from rats ranging in age from -1 day (20 days of gestational age) to 90 days. The magnitude of the response, expressed as a percent increment above control rat GH (rGH) release, rose progressively until it reached a maximum of 209 +/- 5% (mean +/- SE) on postnatal day 12. Thereafter, the response declined to values ranging from 10-30% above control rGH release. In cultured adenohypophyseal cells of rats on postnatal day 12, the effect of TRH was dose related; the effective concentration range was 10(-10)-10(-7) M, with an EC50 of 2.5 +/- 0.6 X 10(-9) M. TRH (10(-8) M) potentiated the GH stimulatory effect of a submaximally effective concentration of human GH-releasing factor-40 (hGRF-40; 10(-9) M) in cultured pituitary cells of developing rats, aged -1 to 30 days, and that of (Bu)2cAMP (5 X 10(-4) M) in cultured pituitary cells of rats aged -1 to 45 days. The rGH response to the combined addition of TRH with either hGRF-40 or (Bu)2cAMP was up to 2 times greater (P less than 0.05) than the sum of the individual responses. When the interaction of TRH (10(-8) M) with multiple concentrations of hGRF-40 (10(-10), 10(-9), and 10(-8) M) was tested in cultured pituitary cells of 4- to 36-day-old rats at 4-day intervals, synergism was least at the lowest and greatest at the highest concentration of hGRF-40; synergistic interaction decreased progressively after 20 days of age to undetectable levels by 36 days. In cultured anterior pituitary cells of 12-day-old rats, maximally stimulatory TRH (10(-7) M) potentiated the GH stimulatory effects of both hGRF-40 and (Bu)2cAMP at concentrations at the EC50 value or greater, with synergism being most pronounced at maximally effective concentrations. Whereas the GH response to the combined addition of maximal hGRF-40 (10(-7) M) and (Bu)2cAMP (1.5 X 10(-3) M) was not greater than that to maximal hGRF alone, TRH potentiated the responses to both secretagogues whether added separately or combined.(ABSTRACT TRUNCATED AT 400 WORDS)     

Respiratory effects of gestational intermittent hypoxia in the developing rat

Intermittent hypoxia (IH), one of the hallmarks of obstructive sleep apnea, occurs more frequently during pregnancy. We hypothesized that IH may lead to persistent postnatal changes in respiratory responses to acute hypoxia and may also lead to adverse effects on spatial function learning as revealed by the Morris water maze. To examine this issue, time-pregnant Sprague-Dawley rats were exposed to IH and room air (IHRA; 21 and 10% O2 alternations every 90 seconds) or to normoxia (RARA) until delivery. Ventilatory and metabolic responses to a 20-minute acute hypoxic challenge (10% O2) were conducted at postnatal ages 5, 10, 15, and 30 days. In addition, spatial task learning was assessed in the water maze at 1 and 4 months of age. Normoxic ventilation was higher at all time points in IHRA rats than in RARA rats (p < 0.01). Peak hypoxic ventilatory responses were attenuated in IHRA rats at 5 days of age and hypoxic ventilatory depression was accentuated at this age as well. However, ventilatory equivalents (minute ventilation/oxygen consumption) revealed significant reductions in peak hypoxic ventilatory responses of IHRA rats and hypoxic ventilatory depression at all postnatal ages (p < 0.01). Acquisition and retention of a spatial task were similar in the IHRA and RARA groups at both 1 and 4 months of age. We conclude that gestational intermittent hypoxia elicits long-lasting alterations in the control of breathing. We postulate that such IH-induced respiratory plasticity may create selective vulnerability to hypoxia during development.     

Thyroid hormones and 5'-deiodinase activity in neonatal undernourished rats.

Undernutrition was induced in rats submitted to food restriction from the fetal stage, and malnutrition was continued after birth until 70 days of life. Body weight was decreased to less than 50%. Plasma T4 and T3 and pituitary TSH content were determined between 8-70 days of life. In control rats, plasma T4 and T3 reached a maximum at 14 and 35 days of life, respectively, and TSH pituitary content at 45 days of life. In undernourished rats, after 8 days of life, plasma T4 and T3 and pituitary TSH content were decreased to about 50% or less, and the pattern of sequential changes observed in control rats was absent or modified. T4 and T3 concentrations were measured in heart, liver, and brain in the fetus (22 days old) and 8, 14, and 23 days after birth, as well as liver and brain 5'-deiodinases (5'D). Hepatic 5'D type I was always decreased in undernourished rats from 8-70 days after birth. Liver and heart T4 and T3 concentrations were decreased in 14-day-old undernourished rats as well as brain T3. Brain 5'D type II was decreased at 8 and 14 days, and total brain 5'D activities at 8 days. These changes occurred during the critical period for brain development (7th to 20th day) during which most processes of myelination take place and T3 brain normal levels are required.     

Duration-dependent effect of transient neonatal hypothyroidism on sertoli and germ cell number, and plasma and testicular interstitial fluid androgen binding protein concentration

The impact of transient neonatal hypothyroidism on growth and function of puberal testis during different milestones of postnatal testicular development was studied in Wistar rats. Rat pups were made hypothyroid for 10, 15, 30, 40 and 60 days of postnatal age from birth by providing 0.05% (W/V) methimazole (MMI) in the drinking water of the mother, from day 1 postpartum till weaning (25 days postpartum) and thereafter in the drinking water. Control rats were raised without MMI treatment. Sertoli cell number and its function was assessed on day 60 postpartum. Sertoli cell number increased consistently in 10, 15, 30 and 40 days transient hypothyroid rats but decreased in rats subjected to continuous hypothyroidism from birth to 60 days postpartum. Rats subjected to continuous hypothyroidism from birth showed spermatogenic arrest at puberty and had only a single layer of spermatogonia. Transient neonatal hypothyroidism for 10 (or) 15 days from birth increased spermatocytes (pachytene and zygotene), spermatids (elongated and round) whereas, that of 30 and 40 days decreases the number of germ cells. Plasma androgen binding protein (ABP) concentration decreased in puberal rats belonging to all groups, whereas the testicular interstitial fluid (TIF) concentration of ABP increased significantly in 10 and 15 days hypothyroid rats while it decreased in all other groups. These findings indicate that the mitogenic activity of Sertoli cell is increased irrespective of the duration of transient neonatal hypothyroidism. However, the functional activity of Sertoli cells (ABP production) in these puberal rats varies depending upon the postnatal period at which the animals were in hypothyroid state.     

Gonadotrophin release in vitro, in the presence and absence of luteinizing hormone releasing hormone, by pituitary glands from ovariectomized and sham-operated immature female rats of various ages

Hemipituitary glands of immature female rats, aged 10, 15, 20, 25, 30 and 35 days and either ovariectomized or sham-operated 5 days earlier, were incubated for 2 h in vitro with or without LH releasing hormone. Concentrations of LH and FSH were determined at the end of the incubations in the incubation media and in the hemipituitary glands, and also in the sera collected at the beginning of the incubation experiments. Results showed that in many instances gonadotrophin release was higher after incubation of glands of ovariectomized rats than with glands of control animals. However, these effects of ovariectomy were much smaller than those observed in vivo and were generally absent in rats of less than 20 days of age. It was concluded that ovariectomy may change the secretory characteristics of the gonadotrophic cells of immature rats but that such changes were largely restricted to immature rats older than 20 days.     

In utero undernutrition reduces diabetes incidence in non-obese diabetic mice

AIMS/HYPOTHESIS: Observational studies in humans suggest that low birthweight may decrease the risk of type 1 diabetes, but the mechanism is unknown. We hypothesised that antenatal undernutrition would decrease the incidence of type 1 diabetes in non-obese diabetic (NOD) mice. MATERIALS AND METHODS: A 40% restriction of energy intake was applied to pregnant NOD dams from day 12.5 to day 18.5 of gestation, resulting in intrauterine growth retardation of offspring. All mice were fed a standard diet after weaning. Control and undernourished female offspring were followed to assess diabetes incidence. Male NOD mice were treated with cyclophosphamide to accelerate development of diabetes. Glucose homeostasis, body composition and pancreatic histology were compared in control and undernourished offspring. RESULTS: Mean birthweight was lower in undernourished than in control mice (p = 0.00003). At 24 weeks of age, the cumulative incidence of spontaneous diabetes in female mice was 73% in control and 48% in undernourished mice (p = 0.003). In cyclophosphamide-treated male mice, antenatal undernutrition also tended to reduce the development of diabetes (p = 0.058). Maternal leptin levels were lower in undernourished dams on day 18.5 of pregnancy (p = 0.039), while postnatal leptin levels were significantly higher in undernourished offspring at 4, 20 and 27 weeks of life (p < 0.05). Beta cell mass was similar in both groups (control = 0.4 mg; undernourished = 0.54 mg; p = 0.24). Histological evidence of apoptosis at 20 weeks was greater in control than in undernourished mice (control = 6.3 +/- 1.4%; undernourished = 4.2 +/- 0.3%, p = 0.05). CONCLUSIONS/INTERPRETATION: Antenatal undernutrition reduces the incidence of diabetes in NOD mice, perhaps via alterations in apoptosis.     

Isolation and characterization of rat fetal Sertoli cells

Sertoli cells were prepared from fetal rats, aged 15, 18, and 21 days. Cultures of these cells can be prepared at a purity of 85% by a method that is widely used to prepare the same cells from postnatal rats. The fetal cells are identical in appearance to postnatal Sertoli cells. Fetal Sertoli cells round up in response to (Bu)2cAMP, but not in response to FSH. Protein synthesis in the cells is not stimulated by (Bu)2cAMP or FSH. However, incorporation of [35S]methionine into secreted proteins appearing in the incubation medium is stimulated by the cyclic nucleotide, but not by FSH. Reproducible patterns for the incorporation of [35S]methionine into cellular and secreted proteins are presented as autoradiograms of one- and two-dimensional electrophoretograms. These autoradiograms show that the response of secreted proteins to (Bu)2cAMP is a general one; most or all proteins participate in the response. No clear differences were observed in the nature of the proteins synthesized when cells from fetal rats of 15, 18, and 21 days of age were compared. Fetal Sertoli cells produced approximately 2 nmol lactate/10(6) cells.h, which is approximately one fifth of the amount produced by postnatal cells. Lactate production was increased by the addition of FSH or (Bu)2cAMP to the medium. Fetal Sertoli cells also synthesize androgen-binding protein, and this activity is not increased by either FSH or (Bu)2cAMP.     

Normal ontogeny of alpha 1-adrenergic receptor in rat liver is thyroid hormone dependent

Postnatal ontogeny of rat liver alpha 1-adrenergic receptor was examined using alpha 1-specific radioligand [3H]prazosin in control and propylthiouracil-treated congenital hypothyroid rats at various ages. Partially purified rat liver membranes prepared by the Neville method had 8-fold purification of 5'-nucleotidase from the crude homogenates from postnatal day 5 to adulthood. [3H]Prazosin binding was typical of an alpha 1-adrenergic receptor, and (-)epinephrine affinity for the [3H]prazosin-binding sites was not altered in the presence of 10(-5) M guanylyl-imidodiphosphate. The receptor density was lower in 5- and 15-day-old rats than in 28-day-old or older rats in both control and hypothyroid groups. (P less than 0.01). At 28-34 days of age, hypothyroid pups had significantly lower alpha 1-receptor density than controls (399 +/- 10 vs. 869 +/- 40 fmol mg protein-1; P less than 0.01). Replacement therapy with daily T4 injection from postnatal days 16-27 restored 54% of the deficit in PTU-treated hypothyroid pups at 28 days. The dissociation constant of [3H] prazosin did not change with advancing age or with different treatment and was consistent at 0.1 nM. These findings indicate that the normal ontogeny of plasma membrane alpha 1-adrenergic receptors is dependent upon thyroid hormone and matures postnatally in rat liver.     

Transient neonatal hypothyroidism alters plasma and testicular sex steroid concentration in puberal rats

The stimulatory and inhibitory effects on testicular steroidogenesis of transient neonatal hypothyroidism from day 1 postpartum through different postnatal developmental events on testis at puberal age (60 days old) were studied in vivo. Hypothyroidism was induced in neonates by feeding the lactating mother or directly with 0.05% methimazole (MMI) through drinking water from the day of parturition to 10, 15, 30, 40 and 60 days, and were killed at day 60 postpartum. Plasma and testicular interstitial fluid (TIF) progesterone, testosterone, dihydrotestosterone (DHT) and estradiol concentrations were assessed. Testis weight and volume significantly increased in rats subjected to 10 and 15 days of hypothyroidism, decreased in rats subjected to 30, 40 and 60 days of hypothyroidism. A consistent increase in Leydig cell number was seen in puberal rats subjected to transient neonatal hypothyroidism but decreased in 60 days hypothyroid rats. Peritubular myoid cell number was consistently decreased in all experimental rats. Leydig cell diameter decreased consistently in all experimental groups. Persistent hypothyroidism (60 days hypothyroid) consistently decreased both plasma and TIF sex steroids. In transient hypothyroid rats, progesterone concentration decreased in both plasma and TIF. Transient hypothyroidism from birth to day 10 postnatal age maintained normal titre of plasma testosterone, whereas a significant increase in TIF testosterone concentration was evident when compared with controls. All other groups of rats subjected to transient neonatal hypothyroidism had consistently low titres of plasma and TIF testosterone. Plasma DHT concentrations in rats subjected to transient neonatal hypothyroidism remained unaltered. However, TIF DHT increased in 10 days     

Effect of chronic undernutrition on hepatocyte insulin receptors in rats

The effect of moderate chronic undernutrition on insulin receptors was studied in male rats, pair-fed 60% of the daily food intake of ad libitum-fed littermates, for 8 weeks. Body weights of undernourished rats were consistently found to be 35% to 40% less than control littermates, with no period of growth arrest at any point in the 8-week study. The binding-displacement curves of labeled insulin to hepatocyte receptors in the two groups in the presence of unlabeled insulin were significantly different (P = .0258 after repeated measures ANOVA). Significantly lower binding was observed in hepatocytes from the undernourished group (P less than .01) at all unlabeled insulin concentrations less than 20 nmol/L. In the absence of any unlabeled insulin, specific binding was reduced from 8.8% +/- 0.7%, (mean +/- SE) in controls, to 7.4% +/- 0.3% in undernourished rats (P less than .01). Half-maximal specific hormone binding to hepatocytes was achieved at a free insulin concentration of 362 nmol/L in the control group, compared with 447 nmol/L in the undernourished group, reflecting an increase of approximately 20%. The hypoglycemic response to intravenous insulin (0.1 U/kg body weight) was tested in a parallel experiment involving seven paired littermate rats, and found to be significantly impaired in the undernourished group (P = .0041 by repeated measures ANOVA).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of protein malnutrition on glycoprotein, protein and lipid synthesis in the rat cerebellum during the period of brain growth spurt

Female Wistar rats were fed a normal-protein diet (25% casein) or a low-protein diet (8% casein) during pregnancy and lactation. The two diets were isocaloric and contained appropriate amounts of mineral salts and vitamins. Pups from dams submitted to the low-protein diet had a lower body weight than normally fed controls as early as on the day of birth, but a difference in cerebellar weight between the two groups was observed only on the 15th postnatal day. Malnutrition had no effect on cerebellar protein concentration, which increased with age in both groups. The cerebellar DNA concentration was higher at 7 and 15 days of age in normally fed rats than in malnourished rats, whereas at 21 days of age it was higher in the malnourished animals. [U-14C]Leucine and [2-3H]mannose incorporation into proteins and lipid synthesis from acetyl coenzyme A (CoA) derived from [U-14C]leucine markedly decreased with age in the cerebellum of rats fed both diets. [2-3H]Mannose incorporation into cerebellar glycoproteins was greater in malnourished rats during the period of brain growth spurt than in normally fed rats at all ages studied. Prenatal and postnatal protein malnutrition had no effect on [U-14C]leucine incorporation into cerebellar proteins or on cerebellar lipid synthesis from acetyl-CoA derived from [U-14C]leucine during the period of brain growth spurt.     

Age-related differences in the growth hormone secretory response to hGHRH 1-44 in male rats from infancy through puberty. In vivo and in vitro studies

The GH secretory response to varying doses (15, 30, 60 micrograms/kg) of sc administered hGHRH 1-44 (or normal saline) was measured in vivo in 10, 20, 30, 40, 50, 60 and 130 days old pentobarbital-anaesthetized, male rats. The 10-min GH level and delta GH were in general significantly greater in older rats (50, 60, 130 days old) than in younger rats (10, 20 days old) following all doses hGHRH. Ten-day-old animals had no significant GH response to any dose of hGHRH tested. delta GH correlated significantly with age (r = 0.36; P less than 0.0001) and Sm-C level (r = 0.29; P less than 0.01) but not with serum testosterone concentrations. Monolayer pituitary cell cultures were established in rats aged 10 to 130 days and were incubated with varying concentrations of hGHRH 1-44 (0.05, 0.5, 5.0, 50 nmol/l or incubation medium). Cultures from 10- and 20-day-old animals had a greater percentage increase over basal GH secretion than other groups at all concentrations of hGHRH tested (P less than 0.05). Age-related differences in the GH secretory response to hGHRH are present in male rats from 10 to 130 days. The in vitro results reported here suggest that the increase in magnitude and sensitivity of the GH response to hGHRH observed in pubertal animals in vivo under pentobarbital anaesthesia is likely due to influences above the level of the somatotrope receptor.     

Routine coagulation tests in newborn and young infants

Background The diagnostic approach to haemostatic defects in the newborn is challenging and requires appropriate interpretation of coagulation tests according to reference values dependent on the postnatal age. Methods This investigation was designed to study the postnatal development of the human coagulation system in newborn infants and to develop appropriate reference ranges for prothrombin time (PT), activated partial thromboplastin time (APTT) and fibrinogen (FBG) according at the day of birth and for the following postnatal period (days 1, 2, 3, 4, 5, 6, from 7 to 10 and from 11 to 44). Results The mean FBG value was already within the adult reference range in newborns at birth, the mean PT value fell within the adult reference range in infants aged 4 days or more, whereas the mean APTT value was still higher than the upper limit of the adult reference range in infants aged between 11 and 20 days. The prevalence of infants with pathological values according to the actual adult reference ranges was limited for FBG (from 24 to 7%), decreased from 92 to 8% in infants aged 0 and 11–20 days for PT, but remained elevated throughout the observational period for APTT (from 94 to 71%). Conclusions The results of the present investigation demonstrate that the actual adult reference ranges for coagulation screening tests, especially PT and APTT, cannot be applied to newborns and young infants.     

Inhibition of rat uterine gland genesis by tamoxifen

We have previously shown that rat uterine gland genesis occurs rapidly and synchronously between postnatal days 9-15. Exogenous estrogens either stimulate or inhibit gland genesis depending on dose and age at administration. We therefore examined the developmental effects of the triphenylethylene antiestrogen tamoxifen, which exhibits both estrogen agonist and antagonist properties, in the postnatal rat uterus. Tamoxifen administered sc in oil on postnatal days 1-5 or days 10-14 caused dose-related inhibition of uterine gland genesis which persisted to day 26 or day 60, respectively. Tamoxifen administered on postnatal days 20-24, which is after the age of normal gland genesis, did not alter the number of preexisting glands. A 24-h exposure to tamoxifen inhibited 17 beta-estradiol (E2)-induced ornithine decarboxylase (ODC) activity measured 6 h after E2 administration in 14-day-old rats. Treatment with tamoxifen before or during the period of gland genesis also reduced uterine responsiveness to a single dose of E2 as measured by both uterine weight gain (after a 24-h exposure on days 14, 19, 22, and 26) and the pattern of E2-induced ODC activity in 26-day-old rats. Control rats respond to E2 with peaks of ODC activity at 6 and 18 h after administration. Treatment with tamoxifen on either postnatal days 1-5 or 10-14 reduced the 18-h peak to approximately half of controls but did not affect the 6-h E2-induced ODC peak. Analysis of both nuclear and translocatable cytosol estrogen receptor in uteri from 26-day-old rats indicate that neither the dissociation constant (KD) nor the number of binding sites was affected by tamoxifen treatment on postnatal days 1-5 or 10-14.     

Effects of undernutrition on glycine metabolism in the cerebellum of rats

Undernutrition is a worldwide problem affecting millions of unborn and young children during the most vulnerable stages of brain development. Total restriction of protein during the perinatal period of life can alter the development of the mammalian fetus and have marked repercussions on development of the central nervous system (CNS). The brain is vulnerable to undernutrition with altered morphologic and biochemical maturation, leading to impaired functions. The focus of this study is to investigate [U-14C]glycine metabolism in undernourished rats submitted to pre- and postnatal protein deprivation (diet: 8% protein with and without addition of L-methionine; control group: 25% protein). Although undernutrition produced a reduction in cerebellar weight and alterations in the DNA concentration, the present study shows that glycine metabolism in this structure is partially protected because the undernourished group with L-methionine did not show modifications in glycine metabolism at all ages studied. However, L-methionine deficiency alters glycine metabolism at 7 and 21 days, but in the adult age both undernourished groups presented no differences in oxidation to CO2, conversion to lipids and incorporation into protein from glycine, compared to the control group.     

Developmental patterns of renal atrial natriuretic peptide receptors: [125I]alpha-rat atrial natriuretic peptide binding in glomeruli and inner medullary collecting tubules microdissected from kidneys of young rats

The ontogenic developmental patterns of atrial natriuretic peptide (ANP) receptors of glomeruli and inner medullary collecting tubules (IMCT) were studied by measuring the specific binding of [125I]alpha-rat ANP 1-28 ([125I]alpha-RANP) to isolated glomeruli and IMCT microdissected from collagenase-treated kidneys of young rats aged from 2 to 35 days post-partum. For glomeruli and IMCT from young and adult animals, total and non-specific binding increased linearly with glomerulus number or tubular length. ANP receptors detected in glomeruli and IMCT from young rats showed the same stereospecifities as those from adult rats for recognition of ANP analogues (alpha-RANP 1-28, ANP 3-28, atriopeptin III and atriopeptin II). The numbers of ANP receptors in glomeruli and IMCT (expressed in terms of 10(-18) mol labelled ANP bound per glomerulus or per mm IMCT length, respectively) exhibited marked variations during postnatal ontogenesis; they were low after birth and rose progressively with age up to the corresponding adult levels (20 +/- 2 X 10(-18) mol.glom-1 and 4.4 +/- 0.8 X 10(-18) mol.mm-1) at the end of the 5th week of postnatal life.     

Hypothyroidism modulates renal antioxidant gene expression during postnatal development and maturation in rat

In the present study effects of 6-n-propyl thiouracil (PTU)-induced hypothyroidism on renal antioxidant defence system during postnatal development (from birth to 7, 15 and 30days old) and on adult rats were reported. Hypothyroidism in rats was induced by feeding the lactating mothers (from the day of parturition till weaning, 25days old) or directly to the pups with 0.05% PTU in drinking water. The activities of Cu/Zn-superoxide dismutase (SOD1) and glutathione peroxidase (GPx) were increased in 30days old hypothyroid rats with respect to their respective controls, on the other hand, levels of translated products and activities of Mn-superoxide dismutase (SOD2) and catalase (CAT) were decreased in hypothyroid rats of all age groups as compared to their respective control rats. SOD1 activity remained unchanged in persistent (PTU-treatment from birth to 90days old) hypothyroid rats as compared to euthyroid. However, a decreased activity of SOD1 was recorded in transient (PTU-treatment from birth to 30days then withdrawal till 90days old) hypothyroid rats with respect to control rats. The mRNA level, protein expression and activity of SOD2 and CAT were significantly decreased in persistent hypothyroid rats as compared to euthyroid rats. The activity of GPx was significantly increased in both persistent and transient hypothyroid rats with respect to euthyroid rats. The present study indicates modulation of antioxidant defence status of rat kidney during postnatal development and maturation by hypothyroidism.     

In vivo studies with growth hormone (GH)-releasing factor and clonidine in rat pups: ontogenetic development of their effect on GH release and synthesis

The demonstration that GH-releasing factor (GRF) stimulates GH synthesis and release in rat pups prompted studies to evaluate the effects on the same indices of clonidine (CLO), an alpha 2-adrenoceptor and potent GH secretagogue, purported to act in adult rats via GRF release. Our first aim was to ascertain whether CLO elicits GH release in rat pups via GRF, and if this is the case, to evaluate the ontogenetic development in 1- to 10-day-old pups of the GH response to acute CLO or GRF administration and, finally, the effects of short term CLO or GRF treatment on plasma and pituitary GH concentrations and on the GH response to an acute challenge with the homologous secretagogue. CLO (15 micrograms/100 g BW, sc) induced a clearcut GH rise in 10-day-old rats but not in pups pretreated with a specific anti-GRF serum. Moreover, unlike GRF (10(-8) M), CLO (10(-6) to 10(-5) M) did not stimulate GH release in vitro from anterior pituitaries of 10-day-old rats. In 1-day-old rats, neither CLO (15 micrograms/100 g BW, sc) nor GRF (20 ng/100 g BW, sc) stimulated GH release, whereas significant GH stimulation was elicited by GRF, but not CLO, in 5-day-old rats and by both secretagogues in 10-day-old rats. Short term treatment with CLO (15 micrograms/100 g BW, sc, twice daily) or GRF (20 ng/100 g BW, sc, twice daily) on postnatal days 1 through 5 did not modify either plasma or pituitary GH concentrations 14 h after the last drug administration, but did so when either secretagogue was administered on postnatal days 5 through 9. Finally, an acute challenge with GRF, but not with CLO, induced a further rise in the already elevated plasma GH levels of pups pretreated from postnatal day 5 through 9, but neither secretagogue did so in pups pretreated from postnatal days 1 to 5. Viewed together, these data indicate that in infant rats CLO releases GH via GRF release and that the somatotropes respond earlier to GRF (5 days) than the GRF-secreting structures do to alpha 2-adrenergic stimulation (10 days). Both GRF and CLO stimulate GH synthesis when administered repeatedly. However, whereas repeated GRF treatment has a priming effect on the somatotropes, CLO does not, probably because of down-regulation of hypothalamic alpha 2-adrenoceptors.     

Skeletal muscle aging in the hind limb of the old male Wistar rat: inhibitory effect of hypophysectomy and food restriction

By age 1 100 days (37 mth) hind leg paralysis was found in 50% of ad libitum fed (control) male Wistar rats, but only 10% of food restricted rats and no hypophysectomized rats of that age had this disease. Gastrocnemius muscle weight declined at a faster rate than whole body weight in old ad libitum fed rats but not in old hypophysectomized or food restricted rats. Light microscopic and ultrastructural changes were studied in the muscles of the hind limbs of 11 control, 5 food-restricted and 5 hypophysectomized rats aged 805 to 1 307 days. Light microscopic changes in muscles involved progressive degeneration demonstrated by the accumulation of adipocytes and degenerative inclusion bodies. The main ultrastructural changes were associated with myofibrillar breakdown. In addition there was thickening of the basal lamina around blood capillaries. However, muscle from hypophysectomized and food restricted rats of the same age range as controls possessed normal morphology with reduced thickening of the capillary basal lamina.