Studies on uptake and catabolism of vascular histamine in spontaneously hypertensive rats

Reduced vascular histamine content is postulated to contribute to increased peripheral vascular resistance in experimental hypertension in rats. Experiments were conducted to examine histamine content, in vitro uptake ability and in vitro catabolism of histamine in blood vessels from 12-week-old spontaneously hypertensive rats (SHR) and age-matched normotensive controls. Histamine content of mesenteric artery and abdominal aorta from SHR was significantly reduced (P less than .05) when compared to Wistar-Kyoto normotensive controls. This finding confirms a similar observation of reduced vascular histamine content in deoxycorticosterone acetate salt hypertensive rats reported from our laboratory. This reduction in histamine content may be more prevalent in arteries because the decrease was not observed in the portal vein from SHR. Uptake of [14C]histamine into mesenteric artery and abdominal aorta was unchanged in SHR compared to Wistar-Kyoto controls. No significant differences between slopes for uptake regression lines were observed for either mesenteric artery or abdominal aorta. Mesenteric artery exhibited a greater capacity of [14C]histamine accumulation than aorta and significant reductions in accumulation of labeled histamine after 20 and 60 min were found in this vessel from SHR. Because metabolism of histamine was inhibited by aminoguanidine, this reduction may reflect diminished retention by histamine storage sites. In vitro I-[14C]histidine uptake was significantly increased in abdominal aorta and iliac artery but not mesenteric artery from SHR. These differences were also present at the later accumulation periods of 20 and 60 min.(ABSTRACT TRUNCATED AT 250 WORDS)