Substance P immunoreactivity in the anterior pituitary gland of the guinea pig

The aim of this study was to demonstrate the presence of Substance P (SP) immunoreactive cells within the anterior pituitary gland of the adult guinea pig. By utilizing the PAP technique of Sternberger, immunoreactive SP-containing cells were visualized in all animals studied. These cells were most dense in the ventral portion of the gland. When adjacent tissue sections were incubated with anti-SP serum and anti-rat TSH serum, it was observed that most, if not all, the SP immunoreactive cells examined also exhibited TSH immunoreactivity. However, not all TSH immunoreactive cells contained SP immunoreactivity. Immunoabsorption controls indicated that the immunohistochemical staining reactions were specific for both SP and TSH. The results of this study indicate that immunoreactive SP is present in the guinea pig anterior pituitary and that this peptide is localized within TSH immunoreactive cells.     

Release of substance P from guinea pig trachea leukotriene D4.

Coordinated studies of leukotriene D4 (LTD4)-mediated contractile responses and LTD4-evoked release of the tachykinin substance P (SP) in both intact and epithelium abraded guinea pig tracheal smooth muscle preparations were performed. A partial contribution by axon reflex mechanisms to the magnitude of LTD4-induced tracheal contractions was suggested by a maximum inhibition of 21% and 28% by 5 x 10(-6) M tetrodotoxin (TTX) in abraded and intact preparations, respectively. SP-induced contractions were antagonized by the SP analog [DPro4DTrp7,9]-SP 4-11 in both types of preparation. The SP analog produced 58% and 72% inhibition of contractile responses to 10(-8) M LTD4 in abraded and intact preparations, respectively. Direct measurement of SP release by radioimmunoassay of the bathing medium showed TTX-sensitive LTD4-evoked release of SP. Inhibition by 5 x 10(-6) M TTX of LTD4-evoked SP release was 77%. The SP antagonist produced greater inhibition of LTD4-evoked contractions (58% in abraded, and 72% in intact preparations) than maximum TTX inhibition of LTD4-evoked contractions (21% in abraded, and 28% in intact). However, LTD4 (10(-8) M)-evoked SP release was at least 77% blocked by maximum doses of TTX. We therefore suggest that an additional agent, released by TTX-insensitive mechanisms, but whose contractile effects are also antagonized by [DPro4DTrp7,9]-SP 4-11, may participate in the LTD4 response.     

Influence of ascorbic acid on in vivo amidation of alpha-melanocyte stimulating hormone in guinea pig pituitary

The effect of ascorbic acid depletion on the amidation of alphamelanocyte stimulating hormone (alpha MSH) was studied in vivo in guinea pig pituitary. After four weeks, the concentration of ascorbic acid was 1.20 +/- 0.11 mumol/g tissue (mean +/- SD) in the pituitary and 0.34 +/- 0.07 mumol/g tissue in the cerebral cortex from the depleted animals versus 7.58 +/- 0.08 and 1.51 +/- 0.32 mumol/g tissue, respectively, in the control animals. In the pituitaries from the animals depleted of ascorbate (N = 4), the relative amount of alpha MSH was reduced to approximately half the values obtained in the control group (from 66.5 +/- 4.6% of total ACTH-related peptides to 31.1 +/- 12.2% (P less than 0.0025]. A concomitant increase (from 5.9 +/- 3.1% to 19.4 +/- 4.3% (P less than 0.004] in ACTH (1-14) (the glycine-extended precursor of alpha MSH) immunoreactivity and a smaller increase in ACTH (1-39) immunoreactivity was observed in the depleted guinea pigs. Gel chromatography and reversed-phase high-performance luquid chromatography showed that the alpha MSH and ACTH (1-14) immunoreactivity was of low molecular weight and partly mono- or diacetylated. Depletion of ascorbic acid had no influence on the degree of acetylation of alpha MSH and ACTH (1-14). It is concluded that depletion of ascorbic acid reduces the in vivo amidation of ACTH (1-14) in the guinea pig pituitary.     

Identification and substance P content of vagal afferent neurons innervating the epithelium of the guinea pig trachea.

Both the nodose and jugular vagal ganglia provide sensory innervation to the airways. The purpose of this study was to localize and characterize the substance P (SP) content of vagal afferent neurons that project specifically to the tracheal epithelium. A retrograde neuronal tracer, fast blue dye or rhodamine-labeled latex microspheres, was instilled into the guinea pig trachea. After 7 d, the nodose and jugular ganglia were removed, sectioned, and prepared for immunocytochemistry. Sections of tracheal mucosa demonstrated that fast blue dye diffused throughout the airway wall, whereas the rhodamine-labeled microspheres, as expected, did not penetrate the basement membrane and were thus localized to the epithelium. When the diffusible fast blue dye was used, approximately 60% of the labeled neurons were found in the nodose ganglia and 40% in the jugular ganglia. By contrast, when the beads were used to label only epithelial nerve fibers, 97 +/- 1% of the tracheal neurons taking up the dye were derived from jugular neurons, 60 +/- 6% of which contained SP immunoreactivity. These studies demonstrate that, in contrast to the submucosa, nerve fibers innervating the epithelium of the trachea are derived nearly exclusively from neurons with cell bodies in the jugular ganglia.     

Maximal expiratory flow in the guinea pig

Using the whole body plethysmograph, the maximal expiratory flow-volume (MEFV) curve was performed in anesthetized-paralyzed guinea pigs with intact chest (n = 7) and in anesthetized, chest-open animals following exsanguination (n = 13). The pressure-volume (PV) curve was also measured. Before and after the MEFV and PV maneuvers, lung volume was determined with a neon dilution method. Peak maximal expiratory flow of 178 ± 7 ml/sec occurring at 83% TLC. After the peak flow, decreased gradually with reducing lung volume. The -static recoil pressure curve was relatively linear up to P_L = 5 cmH₂O. Density-dependence of (helium- was significantly higher than air- ) was found at or above 60% TLC but not at lung volume below 60% TLC. For the chest-open postmortem guinea pig, and TLC decreased while trapped gas volume increased gradually with time after exsanguination, indicating that bronchoconstriction gradually became more severe. The magnitude of this postmortem airway spasm was related to age and anesthetic used.     

Experimental autoimmune myocarditis in the guinea pig

Male and female guinea pigs underwent immunisation with heterologous heart protein (rat heart), complete Freund's adjuvant and pertussis vaccine (immunised) or normal saline (control) at weekly intervals for 6 weeks, and were subsequently studied. In vivo intracardiac pressures, cardiac outputs, blood volumes, in vitro pressure-volume relations, left ventricular collagen contents, light microscopy, direct immunofluorescence, lymphocyte stimulation studies, and serology for circulating anti heart antibody (haemagglutination and radioimmunoassay) were performed. Immunised guinea pigs studied between 5 and 8 weeks following the immunisation protocol demonstrated a 44% increase in LVEDP (p less than 0.005), an increase in right atrial pressure (p less than 0.001), although no change in aortic pressure or cardiac output when compared with controls. Left ventricular weight was increased 20% (p less than 0.001), and in vitro left ventricular volume by 34% (at 8 mmHg distending pressure, p less than 0.001). Lung wet weight was increased 44% (p less than 0.005), and left ventricular collagen content increased 60% (p less than 0.001). Cultured lymphocytes from treated guinea pigs demonstrated a 1.5- to 4.5-fold (dependent upon proximity to last immunisation) increase in radiolabelled thymidine uptake when incubated with guinea pig heart protein compared to controls (p less than 0.001), and circulating anti guinea pig heart antibodies were detected by haemagglutination and radioimmunoassay. Histological examination of the left ventricles revealed inflammatory cell infiltration and myocyte increase to varying degrees in 15 of the 18 treated animals. We conclude that inflammatory, probably immune-mediated, chronic myocarditis can be produced in the guinea pig.     

Acute necrotizing pancreatitis in the guinea pig

The effect of chlorophylla on experimental acute pancreatitis in guinea pigs was investigated. Pancreatitis was induced by intrapancreatic infiltration of a sodium taurocholate solution. Animals treated with intrapancreatic or intraperitoneal injections of chlorophylla showed higher survival rate than untreated controls.Supported in part by a Research Grant from the Chief Scientist, The Ministry of Health, Israel.     

Maximal expiratory flow in the guinea pig

Using the whole body plethysmograph, the maximal expiratory flow-volume (MEFV) curve was performed in anesthetized-paralyzed guinea pigs with intact chest (n = 7) and in anesthetized, chest-open animals following exsanguination (n = 13). The pressure-volume (PV) curve was also measured. Before and after the MEFV and PV maneuvers, lung volume was determined with a neon dilution method. Peak maximal expiratory flow (Vmax) of 178 +/- 7 ml/sec occurring at 83% TLC. After the peak flow, Vmax decreased gradually with reducing lung volume. The Vmax-static recoil pressure curve was relatively linear up to PL = 5 cmH2O. Density-dependence of Vmax (helium-Vmax was significantly higher than air-Vmax) was found at or above 60% TLC but not at lung volume below 60% TLC. For the chest-open postmortem guinea pig, Vmax and TLC decreased while trapped gas volume increased gradually with time after exsanguination, indicating that bronchoconstriction gradually became more severe. The magnitude of this postmortem airway spasm was related to age and anesthetic used.     

Role of substance P in increased airway hypersensitivity following induced stress in a guinea pig asthma model.

Stress is one of the important factors influencing bronchial asthma, but many questions still remain unanswered. To clarify this point we examined airway hypersensitivity before and after electric shock stress and the role of substance P in an animal model of asthma. We determined airway hypersensitivity to histamine and the substance P levels in serum, bronchoalveolar lavage fluid, and bronchial tissue before and after electric shock stress in biphasic asthma-responsive guinea pigs which had been sensitized using ovalbumin. The cell components in bronchoalveolar lavage fluid were also examined. Airway hypersensitivity to histamine (4.9-156 micrograms/ml) was significantly increased (p < 0.01) by electric shock stress. The substance P level was also significantly increased in plasma and bronchoalveolar lavage fluid, but it was significantly decreased in bronchial tissue. The number of eosinophils in bronchoalveolar lavage fluid increased significantly after electric shock stress. These findings demonstrated that airway hypersensitivity to histamine was increased by stress and suggested that substance P, as well as eosinophils, contribute to the pathogenesis of hypersensitivity.     

Pre-synaptic NO-cGMP pathway modulates vagal control of heart rate in isolated adult guinea pig atria

The role of nitric oxide (NO) in the vagal modulation of heart rate (HR) is controversial. We tested the hypothesis that NO acts via a pre-synaptic, guanylyl cyclase (GC) dependent pathway. The effects of inhibiting NO synthase (NOS) and GC were evaluated in isolated atrial/right vagal nerve preparations from adult (550-750 g) and young (150-250 g) female guinea pigs. Levels of NOS protein were quantified in right atria using Western blotting and densitometry. The non-specific NOS inhibitor N- omega -nitro- L -arginine (L -NA, 100 microM, n=5) significantly reduced the negative chronotropic response to vagal nerve stimulation (VNS) at 3 and 5 Hz in the adult guinea pig. This effect was reversed with 1 m ML -arginine. Similar results were observed with the specific neuronal NOS inhibitor vinyl-N5-(1-imino-3-butenyl)- L -ornithine (L -VNIO, 100 microM, n=7). Inhibition of GC with 1H-(1,2,4)-oxadiazolo-(4, 3-a)-quinoxalin-1-one (ODQ, 10 microM, n=7) also significantly reduced the negative chronotropic response to VNS at 3 and 5 Hz in adult guinea pigs. Neither L -NA (n=6), L -VNIO (n=5) nor ODQ (n=6) changed the HR response to cumulative doses of carbamylcholine in adult guinea pig atria suggesting that the action of NO is pre-synaptic. The HR response to VNS was unaffected by L -NA (n=7) or ODQ (n=7) in young guinea pigs and Western blot analysis showed significantly lower levels of nNOS protein in right atria from young animals. These results suggest a pre-synaptic NO-cGMP pathway modulates cardiac cholinergic transmission, although this may depend on the developmental stage of the guinea pig.