Transient hypoparathyroidism induced by synthetic human parathyroid hormone-(1-34) treatment

Daily injections of low doses of a synthetic fragment of human PTH [hPTH-(1-34) have increased iliac trabecular bone volume when used in the treatment of osteoporosis. In approximately 50 patients no major side-effects had occurred. However, during daily sc 100-micrograms injections of the peptide, one patient repeatedly developed parathyroid hypofunction which resolved each time treatment was stopped. Specific immunoglobulin G (IgG) antibodies binding [125I]hPTH-(1-34) were identified in the patient's serum, and positive immunohistochemical reactions were obtained when bovine parathyroid sections were exposed to the patient's IgG. After adsorption with PTH, the patient's IgG, free of anti-PTH antibodies, reacted with renal cell membranes, as demonstrated by indirect immunofluorescence and blocked renal PTH-dependent adenylate-cyclase activation in vitro. These results support the hypothesis that anti-PTH receptor as well as anti-PTH antibodies were generated during hPTH-(1-34) treatment, which led to the development of hypoparathyroidism when their titers were high.     

Immunological comparisons of two synthetic human parathyroid hormone-(1-34) peptides.

The immunological properties of human parathyroid hormone-)1-34) synthesized in accord with the sequence reported by Brewer et al. and the different sequence found by Niall et al. were compared with those of highly purified native human hormone-)1-84). Analyses were performed by radioimmunoassay using 7 anti-bovine parathyroid hormone antisera and bovine parathyroid hormone-)1-34) as tracer. Whereas human parathyroid hormone-(1-34) synthesized in accord with the sequence of Niall et al. was immunologically indistinguishable from native human hormone in all 7 assay systems, striking differences were seen between human parathyroid hormone-(1-34) synthesized in accord with the sequence of Brewer et al. and the native hormone. In none of the 7 assay systems did human parathyroid hormone-(1-34) synthesized in accord with the sequence of Brewer et al. give the same displacement slopes that the reference preparation gave. The observation that immunologic probes easily discriminate between the two different human parathyroid hormone-(1-34) peptides suggests that similar immunologic approaches will be of value in exploring several important issues, particularly those relating to the sequence and conformational properties of human parathyroid hormone and its synthetic peptides and to the question of the existence of isohormonal forms.     

Comparisons of avian renal responses to bovine parathyroid extract, synthetic bovine (1-34) parathyroid hormone, and synthetic human (1-34) parathyroid hormone

The structure of avian parathyroid hormone (PTH) is only partially known, therefore studies of the avian renal responses to PTH have been conducted using bovine parathyroid extract (bPTE), synthetic human PTH (h(1-34)PTH), and synthetic bovine PTH (b(1-34)PTH). In vitro studies indicate that these peptides may have quite different chick kidney receptor binding affinities and adenylate cyclase activation potencies. In the present study, the in vivo renal responses to bPTE, b(1-34)PTH, and h(1-34)PTH have been compared in immature domestic fowl. The following parameters were evaluated: glomerular filtration rates; renal plasma flow rates; urine pH; and fractional excretion of sodium, potassium, chloride, calcium, magnesium, and inorganic phosphate. Overall, the different hormonal peptides elicited qualitatively similar responses: they all were phosphaturic, natriuretic, diuretic, hypomagnesiuric, hypocalciuric, and kaliuretic. This is the first study to show an effect of PTH on renal magnesium transport in avian species. Quantitative comparisons make it clear that bPTE is more natriuretic and diuretic, but less phosphaturic than either b(1-34)PTH or h(1-34)PTH. A temporal dissociation of the phosphaturic response from the other mineral and electrolyte responses suggests that the phosphaturic response is mediated by a separate mechanism.     

Synthetic human parathyroid hormone-(1-34) for the study of pseudohypoparathyroidism

The synthetic amino-terminal fragment of PTH, PTH-(1-34), was recently released for clinical testing of PTH responsiveness. We measured the urinary cAMP and phosphaturic responses to infusion of PTH-(1-34) [3U/kg BW (200 U maximum), iv in 10 min] in patients with pseudohypoparathyroidism and idiopathic hypoparathyroidism, as well as normal subjects. The protocol used data from 5 30-min urine collections and 4 blood samples. Based on the results in 7 patients with pseudohypoparathyroidism (hypocalcemia with increased serum immunoreactive PTH concentrations), 2 patients with suspected pseudohypoparathyroidism, 9 patients with surgical hypoparathyroidism, and 10 normal subjects, this testing protocol differentiated well among these conditions. The patients with pseudohypoparathyroidism had blunted cAMP and phosphaturic responses to PTH-(1-34) administration compared to those of either normal or hypoparathyroid subjects. Induced hypercalcemia failed to restore a normal cAMP response to PTH-(1-34) infusion in 2 patients with pseudohypoparathyroidism. Calculation of the cAMP response to PTH-(1-34) as nanomoles per dL glomerular filtrate during the first 30 min after infusion provided better differentiation among groups than other parameters of cAMP metabolism. Calculating the phosphaturic response as the percent fall in tubular maximum for phosphate reabsorption during the first hour after infusion gave the best degree of statistical separation among groups. We conclude that this new diagnostic agent is effective for the study of renal responsiveness to PTH, and that the protocol described here reliably differentiates patients with pseudohypoparathyroidism from those with hypocalcemia due to other causes.     

重组人甲状旁腺素（1-34）治疗原发性骨质疏松症疗效观察

目的 观察对比重组人甲状旁腺素（1-34）[PTH（1-34）]和降钙素对原发性骨质疏松症的疗效.方法 将20例原发性骨质疏松症患者随机分为试验组和对照组.试验组皮下注射PTH（1-34）20μg,每天1次;对照组肌肉注射降钙素20 IU,每周1次,两组均每日口服钙尔奇D 600mg,连续治疗6个月.所有患者于治疗前后枪测腰椎（L2～L4）、股骨颈骨密度、血钙及血清骨特异性碱性磷酸酶（BSAP）、血清I型胶原交基C端肽（CTX）、PTH等指标及观察有无不良反应.结果 治疗后PTH组和降钙素组腰椎（L2～L4）骨密度变化较治疗前均有明显增加,且有统计学意义.治疗后两组股骨颈骨密度变化较治疗前无明显改善（P〉0.05）,两组间比较无明显差异（P〉0.05）.PTH组BSAP变化值明显高于对照组,两组间比较差异有统计学意义（P〈0.01）;两组治疗后血、尿常规、肝、肾功能均未见明显异常.结论 PTH（1-34）与降钙素都能显著提高腰椎（L2～L4）骨密度,对于原发性骨质疏松症治疗安全有效.     

Preparation of synthetic bovine parathyroid hormone fragment 1-34 for parenteral use in human studies

There is growing interest in use of synthetic parathyroid hormone peptides such as the aminoterminal 1-34 fragment (PTH 1-34) in human studies, since bovine parathyroid extract is no longer commercially available. We found no data concerning how to sterilize and dilute the synthetic bovine PTH 1-34 (bPTH 1-34) to minimize adsorptive losses and maximize conservation of bioactivity. Therefore, we examined adsorptive losses of electrolytically-labelled, biologically-active bPTH 1-34 onto sterile filtration devices (Millex GV, Millipore Corp.) in solutions of 0.1 M acetic acid containing varying human serum albumin (HSA) concentrations (0.1-5.0%, w/v) and varying hormone concentrations (1-50 micrograms bPTH 1-34/ml). We also assessed preservation of bPTH 1-34 bioactivity (canine renal cortical plasma membranes) in diluted, sterile-filtered solutions refrigerated for 4 days. Adsorptive losses were inversely related to bPTH 1-34 concentrations, being least with 50 micrograms bPTH 1-34/ml, at all concentrations of HSA. Losses during filtration were essentially indistinguishable at HSA concentrations of 0.1 - 1.0%, but were, surprisingly, increased by 2.5 and 5.0% HSA. There were no important differences in adsorptive losses among five different lots of Millex-GV filters. Full bioactivity was preserved over 4 days of refrigeration at a bPTH 1-34 concentration of 20 micrograms/ml. The data suggest that bPTH 1-34 should be sterile-filtered at a concentration of greater than or equal to 20 micrograms/ml in 0.1M acetic acid containing 0.1 - 1.0% HSA. Such sterile solutions are stable at 4 degrees C for at least 4 days.     

Human parathyroid hormone-(1-34) increases bone mass in ovariectomized and orchidectomized rats

In intact growing rats, intermittent administration of low doses of PTH increases bone mass. As gonadal hormones are considered to be essential for normal bone growth, the anabolic effect of PTH may be mediated or modified by these hormones. The objective of this research was to determine if the anabolic effect of PTH would be altered in female ovariectomized (OVX) and male orchidectomized (ORCHX) rats. Two weeks after ovariectomy, orchidectomy, or sham operations, 5-week-old rats (eight per group) were given daily sc injections of human PTH (1-34) (8 micrograms/100 g) or vehicle. After 12 days of treatment, all rats were killed; castration was confirmed, and sera, femurs, tibias, and kidneys were collected. Calcium (Ca) and dry weight (DW) of trabecular and cortical bone of distal half-femurs were measured. Female OVX rats were osteopenic compared to their sham-operated controls, as the bone mass of distal femurs decreased while body weight increased. In PTH-treated females, total bone Ca and DW per 100 g BW increased significantly by 16% and 21%, respectively, in sham-operated rats and by 21% and 25%, respectively, in OVX rats compared to the appropriate control values. ORCHX rats were also osteopenic, as the bone mass of distal femurs was significantly decreased compared to that in sham-operated males. However, as body weight also decreased, the bone mass per unit BW was not altered. In PTH-treated males, total bone Ca and DW per 100 g BW increased significantly by 34% and 25%, respectively, in sham-operated rats by 32% and 29%, respectively, in ORCHX rats compared to their appropriate control values. Serum Ca, creatinine, and alkaline phosphatase levels were normal and comparable in all rats. We conclude that PTH increased bone mass in control, OVX, and ORCHX rats, and the anabolic response to PTH is not dependent on gonadal hormones.     

甲状旁腺素1-34对骨质疏松大鼠治疗作用的实验研究

目的探讨甲状旁腺素134(hPTH134)对骨质疏松的治疗作用以及与血钙、磷、维生素D代谢和生长因子的关系。方法用摘除大鼠双侧卵巢的方式制备骨质疏松模型(OVX),实验动物分为4个组:模型对照组(OVX组,摘除大鼠双侧卵巢不作任何处理);hPTH134治疗组(PTH组,摘除大鼠双侧卵巢12w后用hPTH134治疗8w);盐酸雷洛昔芬治疗组(摘除大鼠双侧卵巢12w后用雷洛昔芬治疗8w);假手术组(Sham组,仅切除卵巢周围的脂肪组织约3g,术后12w纳入实验)。应用HOLOGIC第4代双能X线4500W骨密度仪测大鼠腰椎、股骨上段骨密度值(BMD);以骨形态计量学测股骨骨小梁面积、矿化沉积率;用ELISA法测定血清IGF1水平和血清25OHVitD浓度以及血淋巴细胞VitD受体(VDR)含量。结果hPTH134治疗组、盐酸雷洛昔芬治疗组均较OVX组腰椎、股骨上段骨密度增高,组间比较差异有显著性(P<0.01)。hPTH134治疗组较盐酸雷洛昔芬治疗组股骨上段骨密度增高,两组之间差异有显著性(P<0.01)。hPTH134治疗组骨小梁面积明显增加、矿化沉积率增高。hPTH134治疗组、盐酸雷洛昔芬治疗组血清IGF1浓度值、血清25OHVitD浓度值升高,与OVX组比较差异有显著性(P<0.01)。各组血淋巴细胞VDR含量无明显变化,与OVX组比较差异无显著性(P>0.05)。结论hPTH134能够预防腰椎、股骨上段骨密度丢失,使骨小梁面积明显增加、矿化沉积率增高并且血清IGF1及血清25OHVitD浓度值升高,但对VDR含量无明显作用。     

Absence of biological effects of oxidized parathyroid hormone-(1-34) in dogs and rats

Recent studies have shown that oxidation of bovine PTH-(1-34) [bPTH-(1-34)] with H2O2 abolished the vascular effects of PTH in rats and dogs, but the hypercalcemic effect of the oxidized PTH was preserved in the Japanese quail in vivo. These observations seem at variance with previous studies from our laboratory in the isolated perfused canine tibia preparation in which no uptake of immunoreactive PTH or stimulation of cAMP release was demonstrated during infusion of oxidized bPTH-(1-34). The present studies examine the skeletal and renal effects of oxidized PTH-(1-34) in rats and dogs in vivo. Oxidation of PTH with H2O2 reduced its activation of adenylate cyclase by 95% in dog renal cortical membrane. Awake normal dogs were studied before and during the infusion of bPTH-(1-34) or oxidized PTH-(1-34) (4 U/kg X h). With active PTH, ionized Ca+2 rose in each dog (range, 0.7-1.5 mg/dl), while with oxidized PTH, Ca+2 remained within 0.1 mg/dl of the baseline values. Fractional excretion of PO4 rose from 1.58 +/- 0.6% to 29.5 +/- 2.5% with active PTH and from 1.4 +/- 0.4% to 5.7 +/- 1% with oxidized PTH. The latter did not differ from the value in vehicle-infused dogs. Further studies were performed in 30 acutely parathyroidectomized rats. Plasma Ca+2 rose from 8.2 +/- 0.1 to 9.0 +/- 0.3 mg/dl with active PTH (20 micrograms/kg), fell to 7.7 +/- 0.2 with oxidized PTH, and fell to 7.3 +/- 0.3 mg/dl with vehicle. In parathyroid-intact rats plasma Ca+2 increased by 0.9 mg/dl whether given active PTH, oxidized PTH, or vehicle. We conclude that oxidation of bPTH-(1-34) results in loss of both the renal and skeletal effects of PTH in vivo in rats and dogs.     

Response of the parathyroid gland to infusion of human parathyroid hormone-(1-34) [PTH-(1-34)]: demonstration of suppression of endogenous secretion using immunoradiometric intact PTH-(1-84) assay

Alterations in the sensitivity of the parathyroid gland to both stimulative and suppressive stimuli may be partially responsible for skeletal changes that occur with age, estrogen deficiency, osteoporosis, and estrogen treatment of osteoporosis. We sought to define the changes in intact PTH-(1-84) secretion in normal premenopausal and postmenopausal, osteoporotic and estrogen-treated osteoporotic women during the infusion of human (h) PTH-(1-34). hPTH-(1-34) was infused at 0.55 U/kg.h for 24 h, with serum sampling every 4 h. Serum was analyzed for calcium (ionized and total), hPTH-(1-34), and PTH-(1-84). Basal chemistries were no different among groups, except for serum phosphorus, which was highest in osteoporotic women (1.31 vs. 1.07 mmol/L in premenopausal; P less than 0.02), and hPTH-(1-34), which was slightly higher in normal postmenopausal women (19.31 vs. 13.24 ng/L in estrogen treated; P less than 0.02). No differences in PTH-(1-84) were found among groups. hPTH-(1-34) rose similarly in all patient groups, while the calcemic response was somewhat more sluggish in estrogen-treated women, although statistically significant differences were not found. PTH-(1-84) declined rapidly in all patient groups, although estrogen-treated women had a smaller maximal decrease in PTH-(1-84), and the slope of the decremental change in PTH-(1-84) was lower in estrogen-treated women than in osteoporotic or normal postmenopausal women. Untreated osteoporotic women had less suppression of PTH-(1-84) than normal postmenopausal women at every calcium level. Estrogen treatment decreases the calcemic effects of infused hPTH-(1-34) and at the same time reduces calcium-induced suppression of parathyroid secretion. It is possible that such changes in the set-point of the gland contribute to the alterations in bone turnover that result in osteoporosis and the mechanisms by which estrogen prevents bone loss.     

Active variants of human parathyroid hormone (1-34) with multiple amino acid substitutions

We used site-directed mutagenesis to construct 55 single-site variants of rhPTH, a recombinantly-expressed form of human parathyroid hormone (1–34) containing three amino acid changes compared to the natural sequence (ML8, ML18 and FY34). We identified several mutations, at residues Lys¹³, Glu¹⁹, Val²¹, Glu²², Lys²⁷ and Asp³⁰, that increase biological activity by up to 2.5-fold, as measured by stimulation of adenylate cyclase activity in rat UMR-106 cells. We constructed a series of 15 variants in which two to eight substitutions at these positions were combined, and found that the mutations behaved additively, leading to peptides with significantly enhanced potency. The most active combination variant, with six substitutions (KS13, ES19, VQ21, ES22, KQ27 and DN30), is 15 times more active than the parent molecule. However, the extent to which such combinations increase the activity of the peptide depends critically on the identity of the residues at positions 8 and 18. We constructed two of the combination variants in a variety of sequence backgrounds containing different combinations of leucine, methionine and norleucine at positions 8 and 18. Enhancements in potency were significantly reduced when Met or Nle was present at either of these positions, both in UMR-106 cells and human SaOS-2 cells. A corresponding non-additivity was observed in direct measurements of receptor binding affinity on UMR-106 cells. These results suggest that interactions, either direct or indirect, between certain PTH side chains prevent these mutations from behaving in an additive manner.     

Comparison of the effects of synthetic human parathyroid hormone (PTH)-(1-34)-related peptide of malignancy and bovine PTH-(1-34) on bone formation and resorption in organ culture

We have compared the effects of synthetic amino-terminal human PTH-(1-34)-related peptide (PTHrP) of malignancy with those of synthetic bovine PTH-(1-34) in cultures of half-calvariae from 21-day-old fetal rats and of parietal bones from 7-day neonatal mice. Incorporation of [3H] proline into collagenase-digestible protein (CDP) and noncollagen protein (NCP), and percent collagen synthesis (PCS) were measured in both systems. Incorporation of [3H]thymidine and cAMP production were measured in fetal rat calvariae. Production of prostaglandin E2 and I2 and bone resorption, as assessed by release of previously incorporated 45Ca, were measured in mouse parietal bones. The effects of PTHrP and PTH were qualitatively similar. At 96 h CDP in rat calvariae was decreased by PTH at a concentration as low as 0.01 nM, while similar effects were seen with PTHrP at 0.1 nM. Effects on NCP were small, so PCS was reduced. At 24 h [3H]thymidine was not altered, but CDP and PCS were decreased by both PTH and PTHrP. cAMP production was increased in fetal rat calvariae at 30 min. Both PTH and PTHrP increased 45Ca release at low concentrations and prostaglandin production at high concentrations in mouse parietal bones. While PTH was about 10-fold more potent than PTHrP, there was no qualitative difference in the responses. These studies further suggest that PTHrP affects bone through the PTH receptor.     

Comparison of the biochemical responses to human parathyroid hormone-(1-31)NH2 and hPTH-(1-34) in healthy humans.

The 1-31 fragment of human PTH [hPTH-(1-31)NH2] has been shown, like hPTH-(1-34), to have anabolic effects on the skeletons of ovariectomized rats when given intermittently, but, unlike hPTH-(1-34), it does so without affecting serum calcium concentrations and does not activate the protein kinase C second messenger pathway in some target cells. To investigate the biochemical responses to hPTH-(1-31) in humans, we have directly compared it to hPTH-(1-34) during the course of slow infusions of each. Ten healthy adults, five men and five women, aged 26+/-5 yr (range, 22-37), each received 8-h continuous infusions of 8 pmol/kg.h hPTH-(1-34) and hPTH-(1-31) given in random order at least 2 weeks apart. During the infusions there were significant increases in both plasma and urinary cAMP (P < 0.05), but there were no differences in the responses between the two peptides (P = 0.362 for plasma; P = 0.987 for urine). There were also significant phosphaturic and natriuretic responses to the two peptides, which again were not different between peptides. During the infusion of hPTH-(1-34) serum ionized calcium (Ca2+) increased from 1.21+/-0.033 to 1.29+/-0.046 mmol/L (P < 0.01), and endogenous hPTH-(1-84) decreased from 29.6+/-9 to 15.0+/-5.7 pg/mL (P < 0.01), such that there was a negative correlation between them (r2 = 0.45). However, when hPTH-(1-31) was infused, neither serum Ca2+ (1.24+/-0.03 vs. 1.25+/-0.03) nor hPTH-(1-84) (26.8+/-5 vs. 30.7+/-12 pg/mL) was affected. Circulating concentrations of 1,25-dihydroxyvitamin D3 increased from 92+/-42 to 131+/-63 pmol/L (P < 0.05) during infusion of hPTH-(1-34) and from 92+/-27 to 110+/-42 pmol/L (P = NS) during hPTH-(1-31) infusion. There was also a significant increase in the urinary measure of type I collagen degradation of aminoterminal telopeptides from 78+/-45 to 101+/-51 nmol/mmol creatinine (P < 0.05) when hPTH-(1-34) was infused, but it was not affected (68+/-30 vs. 66+/-24 nmol/mmol creatinine) by hPTH-(1-31). Therefore, hPTH-(1-31) appears to be equivalent and equipotent to hPTH-(1-34) in the release of cAMP from target tissues and the renal handling of phosphate and sodium. However, at the doses employed, it does not increase serum calcium, is a weaker stimulator of the 25-hydroxyvitamin D-1alpha-hydroxylase, and does not induce rapid bone resorption.     

Synthetic human parathyroid hormone 1-34 fragment for diagnostic testing

Since bovine parathyroid extract became unavailable for stimulatory testing, the differentiation between hypoparathyroidism and pseudohypoparathyroidism has been made from the measurement of serum parathyroid hormone (PTH) values alone. Responsiveness to PTH can once again be tested with teriparatide acetate, the newly available, biologically active 1-34 fragment of human PTH. The PTH infusion test can be used to confirm a preliminary diagnosis based on serum immunoreactive PTH values, to differentiate between type 1 and type 2 pseudohypoparathyroidism, or to detect a subtle abnormality of calcium metabolism in normocalcemic patients with features suggesting pseudohypoparathyroidism. Of several variables used to express changes in renal metabolism of cyclic adenosine 3',5'-monophosphate (cAMP) or phosphate, the 30-minute change in cAMP excretion per unit of glomerular filtration and the 60-minute percentage fall in the tubular maximum for phosphate reabsorption provide the best discrimination. Teriparatide has a low incidence of adverse reactions and provides an effective diagnostic tool.     

A comparison of the in vivo biochemical responses to exogenous parathyroid hormone-(1-34) [PTH-(1-34)] and PTH-related peptide-(1-34) in man.

PTH-related peptide (PTHrP) is one of the etiological factors associated with hypercalcemia of malignancy in humans and rodents. In both in vivo and in vitro animal systems its actions mimic those of PTH; however, its bioactivity in humans has not previously been assessed. Therefore, we compared the actions of the synthetic human (h) analogs hPTHrP-(1-34) and hPTH-(1-34) when given by iv infusion to 15 healthy subjects, aged 25 +/- 3 yr. Three 12-h test infusions were given to each subject in the order: hPTH-(1-34) at a dose of 8 pmol/kg.h, an equimolar dose (8 pmol/kg.h) of PTHrP-(1-34) (low dose), and a 10-fold higher dose (80 pmol/kg.h) of hPTHrP-(1-34) (high dose). PTH infusion resulted in significant increases from basal values in serum total ionized calcium, urinary phosphate and cAMP, and serum 1,25-dihydroxyvitamin D3 [1,25-(OH)2d3]. No significant increases from basal values in any of these variables were observed during low dose PTHrP infusion. However, a 10-fold higher dose of PTHrP significantly increased serum calcium from 2.36 +/- 0.07 to 2.63 +/- 0.16 mmol/L (P less than 0.003), ionized calcium from 1.22 +/- 0.03 to 1.39 +/- 0.09 mmol/L (P less than 0.003), urinary phosphate from 0.21 +/- 0.19 to 0.31 +/- 0.16 mmol/L glomerular filtrate (P less than 0.05), urinary cAMP from 37 +/- 18 to 53 +/- 28 nmol/L glomerular filtrate (P less than 0.01), and serum 1,25-(OH)2D3 from 29.8 +/- 12.1 to 46.0 +/- 20.3 pmol/L (P less than 0.01). For each variable these changes were statistically equivalent to the increases observed during PTH infusion. The molar concentrations of circulating immunoreactive PTH-(1-34) and PTHrP-(1-34) (at the higher dose) achieved during infusion were at a ratio of 1:3. These results suggest that the in vivo actions of synthetic hPTHrP-(1-34) are comparable to those of hPTH-(1-34), but its biological activity after infusion may be less than that of hPTH-(1-34). Moreover, the increased concentrations of serum 1,25-(OH)2D3 observed with administration of hPTHrP-(1-34) are unlike the changes seen in hypercalcemia of malignancy in which levels of this vitamin D metabolite are frequently depressed.     

Comparative study on the cardiac actions of bovine parathyroid hormone (1-34)

The cardiac stimulatory effects of bovine parathyroid hormone (1-34) [bPTH-(1-34)] were studied on isolated atria and ventricular strips from cobra snakes (Naja naja), ducklings (Anas platyrhynchos), pigeons (Columba livia), Japanese quails (Coturnix coturnix japonica), laboratory rats (Rattus norvegicus), and dogs (Canis familiaris). In all atrial preparations, bPTH-(1-34) caused positive chronotropism. This suggests that the chronotropic effect of PTH is ubiquitous among the terrestrial vertebrates. Only the atria of cobra snakes and ducklings gave positive inotropic responses to PTH. No ventricular preparations showed significant response to bPTH-(1-34). This suggests the absence of cardiac stimulatory PTH receptors in the ventricles. Dog papillary muscle, however, showed slight but significant responses to bPTH-(1-34). The reason for this discrepancy between the responses of papillary muscles and the ventricular strips to PTH is unknown.     

Anabolic and catabolic regimens of human parathyroid hormone 1-34 elicit bone- and envelope-specific attenuation of skeletal effects in Sost-deficient mice

PTH is a potent calcium-regulating factor that has skeletal anabolic effects when administered intermittently or catabolic effects when maintained at consistently high levels. Bone cells express PTH receptors, but the cellular responses to PTH in bone are incompletely understood. Wnt signaling has recently been implicated in the osteo-anabolic response to the hormone. Specifically, the Sost gene, a major antagonist of Wnt signaling, is down-regulated by PTH exposure. We investigated this mechanism by treating Sost-deficient mice and their wild-type littermates with anabolic and catabolic regimens of PTH and measuring the skeletal responses. Male Sost(+/+) and Sost(-/-) mice were injected daily with human PTH 1-34 (0, 30, or 90 μg/kg) for 6 wk. Female Sost(+/+) and Sost(-/-) mice were continuously infused with vehicle or high-dose PTH (40 μg/kg · d) for 3 wk. Dual energy x-ray absorptiometry-derived measures of intermittent PTH (iPTH)-induced bone gain were impaired in Sost(-/-) mice. Further probing revealed normal or enhanced iPTH-induced cortical bone formation rates but concomitant increases in cortical porosity among Sost(-/-) mice. Distal femur trabecular bone was highly responsive to iPTH in Sost(-/-) mice. Continuous PTH (cPTH) infusion resulted in equal bone loss in Sost(+/+) and Sost(-/-) mice as measured by dual energy x-ray absorptiometry. However, distal femur trabecular bone, but not lumbar spine trabecular bone, was spared the bone-wasting effects of cPTH in Sost(-/-) mice. These results suggest that changes in Sost expression are not required for iPTH-induced anabolism. iPTH-induced resorption of cortical bone might be overstimulated in Sost-deficient environments. Furthermore, Sost deletion protects some trabecular compartments, but not cortical compartments, from bone loss induced by high-dose PTH infusion.     

Actions of synthetic parathyroid hormone-related protein(1-34) on the isolated rat kidney

The isolated perfused rat kidney was used to study the effects of parathyroid hormone-related protein (PTHrP) on renal cyclic AMP (cAMP) and electrolyte excretion. A perfusate of PTHrP(1-34) increased cAMP excretion from 0.14 +/- 0.09 (S.E.M.) nmol/l glomerular filtrate (GF) in controls to 24.67 +/- 5.14 (P less than 0.01) and decreased calcium excretion from 0.278 +/- 0.033 to 0.162 +/- 0.011 mumol/l GF (P less than 0.01). Human PTH(1-34) (0.7 nmol/l) caused no significant change in calcium excretion, whilst the rise in cAMP excretion was similar to that with PTHrP. PTHrP(1-34) (7 nmol/l) further increased cAMP production to 366.7 +/- 100.8 nmol/l GF (P less than 0.01), higher than the rise with hPTH(1-34) (7 nmol/l) which was 76.7 +/- 46.8 (P less than 0.05). With the higher concentrations of both peptides (7 nmol/l), calcium excretion was further reduced to 0.090 +/- 0.009 mumol/l GF (P less than 0.01), whilst phosphate excretion increased with both PTHrP and PTH. PTHrP (7 nmol/l) caused a fall in urinary pH compared with controls (P less than 0.05). At low and high concentrations of both hormones, urinary pH was lower with PTHrP than hPTH (P less than 0.01). Thus PTHrP, like PTH, acts on the kidney to increase cAMP and phosphate excretion and reduce calcium excretion, but PTHrP may be more effective. Disparate effects on urinary pH could be reflected in the clinical features of humoral hypercalcaemia of malignancy.     

Comparison between recombinant human parathyroid hormone(1-34) and elcatonin in treatment of primary osteoporosis

Objective:To evaluate the efficacy and safety of rhPTH(1-34) vs.elcatonin.Methods:Sixty palients with primary OP were randomly divided into two groups according to the ratio of 3:1.rhPTH(1-34) group(PTH group) was treated with subcutaneous injection of rhPTH(1-34) 20 μg daily for 18 months,and the elcalonin group(CT group) was treated with intramuscular injection of elcatonin 20 U weekly for 12 months.Bone mineral density(BMD) of the lumbar spine 2-4(L_(2-4))and femoral neck,serum calcium and phosphorus,urinary calcium,serum hone specific alkaline phosphatase(BSAP).and urinary c-terminal telopeptides of type Ⅰ collagen/creatinine(uCTX-Ⅰ /Cn were tested at baseline,and 6.12.and 18 months after treatment.Results:In PTH group.HMD of L_(2-4),at 6,12.and 18 months,BDM of Femoral neck at 18 month,BSAP at 6 and 12 months and uCTX- Ⅰ /Cr at 6.12 and 18 months were all significantly raised.In CT group.HMD of L_(2-4) at12 month and that of femoral neck at 12 and 18 months were significantly elevated,while HSAP was significantly decreased at 12 and 18 months,and no significant difference on CTX- Ⅰ /Cr was observed.When BMD growth and growth rate between two groups were compared.PTH group had better improvement in L_(2-4) BMD and growth rate than CT group at 6.12.and 18 months.BMD growth and growth rale of femoral neck al 12 month and its growth at 18 month in CT group were higher than in PTH group,hut there was no significant difference between two groups regarding the growth rates at 18 month.Besides,there were no significant differences regarding the rales ol adverse reactions between two groups.Conclusions:rhPTH(1—34),is safe and effective in the treatment of primary OP.It is superior to elcatonin in improving vertebral HMD at onset time,growth rate and growth range,but inferior to elcatonin at HMD of femoral neck.