In vivo evidence for B-1-receptor synthesis induction by heat stress in the rat

A hypotensive effect of intravenously injected [des-Arg(9)]-bradykinin was found in Wistar rats following acute heat stress. This effect was similar to that of intravenously injected bradykinin and was observed 6, 18 and 24 h following an increase in rectal temperature at 42 degrees C for 20 min (H6, His and H24 groups, respectively). In contrast, [des-Arg(9)]-bradykinin had no effect on blood pressure in control or sham conditions, early on (3 h) or later on (72 h) after heat stress (Ctl, H3 and H72 groups, respectively), while the response to bradykinin was maintained. The hypotension induced by [des-Arg(9)]-bradykinin in groups H6, His and H24 was comparable to that induced in rats pretreated with a small amount of endotoxin 24 h earlier (LPS group). The hypotensive response in group H24 was totally blunted by [des-Arg(10)]-Hoe 140 (a potent B-1 receptor antagonist) infused at a rate of 10 mu g min(-1). These results suggest that heat stress induces the synthesis of vascular B-1 receptors in the rat.