title: Increase of plasma renin activity after subcutaneous application of compound 48/80 in the rat.
abstract: Subcutaneous (s.c.) administration of compound 48/80 (3.0 mg/kg) to conscious rats produced a time-dependent long-lasting increase of plasma renin activity (PRA). A dose-related increase of the hematocrit was also observed after injection of compound 48/80. The onset of the hematocrit increase preceded that of PRA increase. Pretreatment with a dose of more than 20 mg/kg of histamine H1-receptor antagonists such as tripelennamine or diphenhydramine prior to the injection of compound 48/80 (3.0 mg/kg s.c.) attenuated or abolished the effects of compound 48/80 on PRA, hematocrit and plasma extravasation. Pretreatment with cimetidine (histamine H2-receptor antagonist, 40 mg/kg i.p.) had no effect on these plasma variables. The increase of PRA caused by s.c. administration of compound 48/80 was not affected by the pretreatment with propranolol (beta-adrenoceptor antagonist, 10 mg/kg i.p.), which completely inhibited the isoproterenol (0.5 mg/kg s.c.)-induced PRA increase. Administration of compound 48/80 did not induce a significant PRA increase in the nephrectomized rats although the increase of hematocrit following s.c. administration of compound 48/80 persisted despite the absence of kidneys. S.c. administration of compound 48/80 (3.0 mg/kg) led to a significant decrease of histamine content at the site of injection and to a significant increase in plasma histamine concentration without affecting arterial blood pressure. The present data suggest that s.c. administration of compound 48/80 stimulates the release of histamine from cutaneous mast cells, which cause an increase in vascular permeability to plasma protein via the stimulation of histamine H1-receptors, then leads to hypovolemia. The resulting hypovolemia may directly stimulate the juxtraglomerular cells of the kidney to release renin.
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002199:Capillary Permeability / Q000187:drug effects; D002927:Cimetidine / Q000494:pharmacology; D004155:Diphenhydramine / Q000494:pharmacology; D006400:Hematocrit; D006632:Histamine / Q000032:analysis; D007279:Injections, Subcutaneous; D008297:Male; D009392:Nephrectomy; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012083:Renin / Q000097:blood*; D003189:p-Methoxy-N-methylphenethylamine / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D003189:p-Methoxy-N-methylphenethylamine; D002927:Cimetidine; D006632:Histamine; D004155:Diphenhydramine; D011433:Propranolol; D012083:Renin