Mechanism of the Immediate Capillary Stress Response

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Abstract
Two possibilities may be considered for the mechanism of the immediate capillary stress response: the direct nervous origin, and the humoral. The latter was investigated in this study. Immediate capillary stress response was found in the absence of the adrenal, pituitary or thyroid glands, and after removal of both the adrenals and the pituitary. Among the 10 physiologic substances considered as playing a potential role in this phenomenon, three were found to possess capillary activity. Vasopressin as well as oxytocin increases capillary resistance. Histamine gives rise to a biphasic response, involving a decrease of capillary resistance (primary effect) followed by an increase (due to vasopressin elicited by histamine). By means of these substances it is possible to duplicate the immediate capillary stress response. During the immediate capillary response plasma has antidiuretic and chloruretic properties—a finding compatible with an increased vasopressin concentration and with the assumption that vasopressin is discharged rather regularly in the first phase of the stress response. The immediate capillary stress response seems to be the result of an interplay between vasopressin-oxytocin, and histamine. Species and individual differences in the sensitivity to these substances may account for the various patterns of the capillary response. The possible significance of the immediate capillary response and of the increased vasopressin activity in some clinical conditions is discussed.