Effects of calcitonin gene-related peptide on canine cerebral artery strips and the in-vivo vertebral blood flow in dogs

Summary The effects of calcitonin gene-related peptide (CGRP) on canine cerebral arteries and on vertebral blood flow were investigated in-vivo and in-vitro and the findings compared with the effects of vasoactive intestinal peptide (VIP) and substance P. Administration of CGRP into the vertebral artery caused a dose-dependent and long-lasting increase in blood flow. The in-vivo vasodilatory effects of substance P and VIP were short-lasting. CGRP (0.1 to 100 nmol/l) elicited a concentration-dependent relaxation of the isolated middle cerebral and basilar arteries when the tissues were precontracted by exposure to prostaglandin F₂ (PGF₂). This effect was not antagonized by propranolol, atropine, tetrodotoxin, (N-Ac-Tyr¹, D-Phe²)-growth hormone-releasing factor(1–29)-NH₂ or (D-Pro², D-Trp^7,9) substance P. CGRP also reduced concentration-dependently the contraction of cerebral arteries induced by KCl or 9,11-epithio-11,12-metano-thromboxane A₂ (STXA₂). Mechanical removal of the endothelium did not abolish the vasodilatory response to CGRP. In PGF₂-contracted canine cerebral arteries, VIP (0.1 to 100 nmol/l) was less potent a vasodilator than CGRP. At low concentrations (0.01 to 1 nmol/l) substance P elicited a rapid and short-lasting relaxation, and in the absence of endothelium this relaxation disappeared. These findings are clear evidence that CGRP modulates vascular tone.     

Renal and hormonal effects of alpha1-adrenoceptor blockade by bunazosin in essential hypertension

Summary The renal and hormonal effects of the ₁-adrenoceptor blocker bunazosin were examined in 6 patients with essential hypertension. Oral bunazosin for 4 to 12 weeks significantly decreased mean blood pressure by 10%, increased effective renal blood flow and creatinine clearance by 34% and 37%, respectively, the plasma norepinephrine concentration was elevated by 60%, and the plasma atrial natriuretic peptide level was lowered by 22%. The plasma renin activity and aldosterone concentration were unchanged. Thus, a moderate reduction in blood pressure was produced by bunazosin treatment while maintaining renal perfusion.     

Humoral and cellular effects of the K+-channel activator cromakalim in man

Summary The effect of cromakalim, a K⁺-channel activator, on the plasma renin-angiotensin-aldosterone system, catecholamines and -atrial natriuretic peptide, and on the intraerythrocyte concentration and transmembrane fluxes of Na⁺ and K⁺ has been investigated in 18 normal male subjects, in a double-blind parallel study. After a run-in period on placebo for 1 week, the subjects were treated either with placebo (n=6) or cromakalim (n=12) for 1 week.Plasma renin activity was significantly increased during cromakalim. No effect of cromakalim on plasma angiotensin II, aldosterone, adrenaline, noradrenaline and -atrial natriuretic peptide was demonstrated. The intra-erythrocyte K⁺ concentration was decreased during cromakalim administration and Ca²⁺-dependent K⁺-channels in red blood cells were increased.     

Synthesis and acid ionization constants of cyclic cystine peptides

Cyclic peptide disulfides of the general formula were synthesized from the corresponding peptide derivatives [Boc-Cys(Trt)(Gly)-_n-Cys(Trt)-OBu^t] by oxidation with iodine in methanol and by subsequent removal of the terminal groups with trifluoroacetic acid. Acid ionization constants of the obtained peptides were determined by potentiometric titration in aqueous KCl (0.1 mol/L) medium. All compounds have two dissociable hydrogens, corresponding to carboxyl (pK¹= 2.35–2.84) and to terminal amino group (pK₂= 5.61–6.93); pK₁, values show first an upward and then a downward trend with the increase in ring size; the opposite is true for pK₂, values. These trends could be tentatively attributed to the intramolecular salt bridge (-COO——-NH⁺₃-) formation.     

Effects of atrial natriuretic peptide on DNA synthesis and NADPH diaphorase activity in epitheliocytes and smooth muscle cells of the respiratory tract in newborn albino rats

Newborn rats received single intraperitoneal injections of atrial natriuretic peptide (1-28) in a dose of 3.2×10_-8 mol/kg on day 6 of life. Autoradiography with ³H-thymidine showed that the peptide inhibited DNA synthesis in smooth muscle cells of the respiratory tract. Pretreatment with nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester attenuated, but did not abolish the effect of atrial natriuretic peptide (1-28). Histochemical assay for NADPH diaphorase showed that nitric oxide constitutively produced in the epithelium is involved in the growth-inhibitory effect of atrial natriuretic peptide (1-28) on proliferating smooth muscle cells.     

Opioid peptides selective for mu- and delta-opiate receptors reduce calcium-dependent action potential duration by increasing potassium conductance

We suggest that both mu- and delta-opiate receptors on dorsal root ganglion neuron somata are coupled to voltage- and/or calcium-dependent potassium channels since opioid peptide decreases of calcium-dependent action potential duration were: (1) not associated with a change of resting membrane potential or conductance; (2) accompanied by an increase in action potential after-hyperpolarization, and (3) blocked by intracellular injection of the potassium channel blocker cesium [18]. In contrast, norepinephrine [4] and cadmium [9], which have been reported to act on voltage-dependent calcium rather than potassium channels, shortened action potential duration and decreased after-hyperpolarization amplitude, an action not blocked by intracellular iontophoresis of cesium.     

Establishment and Characterization of Cell Lines from Human Adenovirus Type 12-induced Murine Tumors Producing Endogenous Virus Particles

Two cell lines designated IC KMS and D KMS were established from human adenovirus type 12 induced tumors of C3Hf/OK mouse. The cell lines retained the characteristics of the original tumor i.e., production of numerous C type and intracisternal A-type particles, integration of Adl2 El region DNA and amplification of the myc gene family. Chromosomal analysis revealed chromosome aberrations in both IC KMS and D KMS cells. The modal chromosome number of IC KMS cells was 54 and that of D-KMS cells was 48. Metacentric chromosomes and mini-chromosomes were found. Trisomy of chromosome 3, 7 and 12 was seen frequently in D KMS cells. Although DNA aneuploidy was revealed by flow cytometry, the DNA indices of these cells showed no relation to the copy number of integrated Adl2 DNA. These cells have been propagated by serial culture during the past 17 months. Production of endogenous virus particles is a unique characteristic of IC KMS and D KMS cells. These cell lines would be useful materials for examining the contribution of Adl2 carcinogenesis to activation of endogenous virus particles, and also the correlation between Adl2 carcinogenesis and cancer related genes. Acta Pathol Jpn 42: 242-248, 1992.     

Hormone changes induced by 37.5-h head-down tilt (−6°) in humans

Endocrine regulation of hormones and electrolytes during 37.5 h of –6° head down tilt (HDT) was studied in 13 men. The acute effects of simulated weightlessness are today well documented, but no study has been made concerning the hormone changes between 12 h and 2 days of HDT. Plasma volume showed a maximal increase of 9.23 (SEM 1.97) % after 6.5 h (P<0.01) and had returned to prestudy levels after 13.5 h of HDT. From 1.5 h to 4 h of HDT, C-terminus and N-terminus atrial natriuretic peptide (ANP) concentrations in plasma were increased by about 50% (P<0.01) and thereafter declined to pre-HDT levels. Plasma renin activity (PRA) was decreased by 47% (P<0.05) after 4 h of HDT; PRA increased after 23.5 h to 60%; noradrenaline concentration decreased immediately and remained low up to 37.5 h. Diuresis and natriuresis were evident during the 1st day of HDT, resulting in a marked increase in the urinary Na⁺. These results showed that the initial hormone (ANP, PRA) changes during HDT did not last more than 13.5 h and that after 24 h a new state would seem to have been established to adapt the body to hypovolaemia.     

Intraduodenal neuropeptide levels,but not plasma levels,vary in a cyclic fashion with the migrating motor complex

The neurohormonal control of the migrating motor complex (MMC) is not fully understood. The hypothesis of the present study was that neuropeptide levels might vary with the different phases of the MMC and that a similar variation might be found in the secretions of the gastrointestinal tract. Thus, plasma and intraduodenal concentrations of vasoactive intestinal peptide (VIP), somatostatin (SOM), substance P (SP) and neurokinin A (NKA) were determined by radioimmunoassay every 10 min during two complete MMC cycles in eight male subjects. For comparison, plasma motilin (MOT) concentrations were measured. Plasma concentrations of MOT (mean peak value ± SEM; 39 ± 6 pmol L^?1), but none of the neuropeptides studied, showed a cyclic variation in plasma with the different phases of the MMC. Peak intraduodenal concentrations of VIP (79 ± 23 pmol L^?1),?SOM (2437 ± 432 pmol L^?1) and SP (718 ± 326 pmol L^?1) occurred at or at the time point before the onset of phase III of the MMC. No such correlation was observed for NKA. These results demonstrate that intraduodenal but not plasma concentrations of the neuropeptides VIP, SOM and SP show an association with phase III of the MMC. The biological relevance of this finding is yet unclear, but the results raise the possibility that gut neuropeptides may regulate fasting motility through a luminal release.     

Effect of prostaglandin E2 on agonist-stimulated cAMP accumulation in the distal convoluted tubule isolated from the rabbit kidney

The effects of calcitonin, vasoactive intestinal peptide (VIP), parathyroid hormone (PTH) and isoprenaline on intracellular cAMP accumulation were determined in the distal tubule (DCT) microdissected from collagenase-treated rabbit kidney. In DCTb (the initial bright portion) calcitonin (10 ng/ml) elicited a highly reproducible response 203.7±19.1 fmol cAMP mm^–1 4 min^–1 (SE, N=13) whereas VIP-induced cAMP accumulation was less and more variable from one experiment to another (1 M, 97.2±17.8 fmol mm^–1 4 min^–1, SE, N=12). When used in combination, these two agonists were non-additive, indicating stimulation of a single pool of cAMP in DCTb. In DCTg, (granular) which consists of at least two cell types, PTH (100 nM) elicited a marked, reproducible accumulation of cAMP (154.3±27.0 fmol mm^–1 4 min^–1; SE, N=5). Isoprenaline (1 M) and VIP (1 M) induced much smaller increases in cAMP levels 20.9±2.7 and 29.4±4.1 fmol mm^–1 4 min^–1 (SE, N=5) respectively, and, when used in combination, were non-additive, demonstrating that VIP and isoprenaline are active on the same cell type. In DCTb, prostaglandin E₂ (PGE₂) inhibited both calcitoninand VIP-stimulated cAMP accumulation (calcitonin 57.8±2.7% inhibition, SE, N=16; VIP, 80.6±2.1% inhibition, SE, N=5). The EC₅₀ values for calcitonin were 1.21±0.33 ng/ml and 1.83±0.25 ng/ ml (SD, N=3) in the absence and presence of PGE₂ (300 nM) respectively with an IC₅₀ for PGE₂ of 26.3±6.3 nM (SE, N=4). In contrast, no effects of PGE₂ were seen in DCTg vis à vis PTH, isoprenaline or VIP. The percentage inhibition of calcitonin-stimulated cAMP accumulation by PGE₂ was of the same order in the presence of isobutylmethylxanthine (an inhibitor of all types of phosphodiesterase), Ro 20-1724 (inhibitor of low-K _m cAMP-specific phosphodiesterase) or in the absence of inhibitor. Preincubation of DCTb with pertussis toxin for up to 8 h in different experimental conditions did not relieve the inhibition by PGE₂. Protein kinase C activation by phorbol ester did not attenuate calcitonin responses. These data demonstrate that the inhibition by PGE₂ of cAMP production is restricted to the initial portion (DCTb) of the distal convoluted tubule and is effective on both calcitonin and VIP responses. When tested in the presence of Ro 20-1724, ionomycin, A₁-adenosine, ₂-adrenergic and muscarinic agonists were without effect on calcitoninand PTH-stimulated cAMP accumulation in DCTb and DCTg respectively.