Spermine decreases peripheral vascular resistance in the dog and relaxes the isolated aorta of the guinea pig.

Abstract

Polyamines, found in all nucleated cells, have been shown to relax uterine, gastrointestinal, and respiratory tract smooth muscle. When parenterally administered to the rat or dog they cause hypotension. To determine the range of the relaxing effect of polyamines on smooth muscle and the mechanism of the hypotensive effect anaesthetised dogs were infused with increasing intravenous bolus doses of spermine while cardiovascular measurements were made. At doses of greater than or equal to 2 mg X kg-1 spermine a reversible hypotensive effect was produced that is accounted for by changes in peripheral vascular resistance. It is unlikely that this effect was due to the known propensity of polyamines to release histamine because the hypotensive action of 2 mg X kg-1 spermine was unaltered by pretreatment with the H1 and H2 blockers, diphenhydramine and cimetidine. Evidence that the spermine effect is not mediated by circulating agents was shown by the ability of spermine to relax the precontracted guinea pig isolated aorta. These results in vascular smooth muscle may be added to those in other types of smooth muscle shown to be relaxed by polyamines; the polyamine effect on smooth muscle may be ubiquitous. These data also raise the possibility that changing concentrations of tissue polyamines may play a role in the regulation of tissue blood flow.