Remodeling of capillary network in left ventricular subendocardial tissues induced by intravenous vasopressin administration.

Abstract

The question of whether the coronary vasospasm induced by intravenous administration of vasopressin produces any remodeling of the capillary network in the left ventricle was investigated. To this end, cardiac tissues obtained from vasopressin-injected rats were stained to allow capillary counting and for basic fibroblast growth factor (bFGF). Nine male Donryu rats were divided into three groups that received, respectively, 0.25 ml of saline containing 0, 0.5, or 1.0 U/kg vasopressin injected into the tail vein once daily for 4 days. Rats were killed 30 days after the last injection. Two additional rats each received a single intravenous injection of 1.0 U/kg vasopressin and were killed 24 hours later. The left ventricles were removed and 16- or 10-micron frozen sections were cut for differential staining and distribution of bFGF, respectively. Differential staining was used to classify the capillary portions, and bFGF was identified by immunohistological staining. Compared with the control group, total capillary density was increased in both vasopressin-treated groups, capillary to myocyte ratio was increased, and the capillary domain areas decreased in the three capillary portions. Arteriolar and intermediate capillary portions increased, while the venular capillary portion decreased. In rats killed 24 hours after vasopressin injection, a considerable amount of bFGF could be demonstrated immunohistochemically in the ventricular tissues, and the punctate distribution of bFGF was still found in rats killed 30 days after treatment. A remodeling of capillary network which would increase the oxygen transport capacity to cardiac tissues was produced in left ventricular tissues by intravenous injection of vasopressin. bFGF located around capillaries and in the interstitial space may have been involved in the capillary remodeling.