Evaluation of the contribution of mast cell mediators to the hypotensive activity of various peptides in rats.
We have tested the effects of intravenous injections of substance P (SP), bradykinin (BK), somatostatin (SS) and vasoactive intestinal peptide (VIP) on the blood pressure, histaminemia and hematocrit in pentobarbital-anesthetized rats. The four peptides elicited a decrease of the mean arterial blood pressure which varied both in amplitude and in duration depending both on the peptide and on the doses utilized. The hypotensive effects of SP and VIP were more persistent than those caused by BK or SS. Only SP evoked an increase of histaminemia. Both SP and BK caused an increase of hematocrit. The change of hematocrit was more prominent and of longer duration after Sp than after BK. Pretreatment of rats with the antiinflammatory drug dexamethasone inhibited markedly the changes of blood pressure, histaminemia and hematocrit caused by SP. The hypotensive effects of BK, SS and VIP as well as the transient change of hematocrit evoked by BK were not affected by dexamethasone. The results suggest that part of the hypotensive activity and changes of hematocrit evoked by SP in rats is due to the release and action of histamine and possibly of other vasoactive substances, of mast cell origin. The results also indicate that mast cell mediators, particularly histamine, are unlikely to be instrumental in the hypotensive activity of BK, SS or VIP in rats.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D001920:Bradykinin / Q000494:pharmacology*; D003907:Dexamethasone / Q000494:pharmacology; D005768:Gastrointestinal Hormones / Q000494:pharmacology*; D006400:Hematocrit; D006636:Histamine Release / Q000187:drug effects*; D008297:Male; D008407:Mast Cells / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013004:Somatostatin / Q000494:pharmacology*; D013373:Substance P / Q000494:pharmacology*; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology*
D005768:Gastrointestinal Hormones; D013373:Substance P; D014660:Vasoactive Intestinal Peptide; D013004:Somatostatin; D003907:Dexamethasone; D001920:Bradykinin