Measured with heated thermocouples, intravenous ACTH was found to increase adrenal blood flow within 1 rain in anaesthetized as well as in conscious dogs. Repeated injections continued to increase flow at a time when corticoid secretion was no longer increasing. Hypotension induced by bleeding and vasoconstriction elicited with vasopressin produced less substantial reductions in adrenal than in renal and thyroida] blood flow. Thyroida] blood flow failed to respond to thyrotrophic hormone within the observation period. --The rubidium s6 method yielded after ACTH the same results in dogs as those obtained by SA~I~ST~IN in rats.
The relationship of secretory rate to blood flow in endocrine glands is imperfectly known. Evidence has been found for (BALsO~R 1953; W~IG~T 1963) and against (HA~T~A~N and Bt~OWNELL 1955; McDonALD and I%EIC~ 1959) increased adrenal blood flow after ACTH, probably owing to variations in the experimental methods. Some methods are open to objection; for instance, adrenal vein cannullation will in many cases alter the rate of flow. SAPIRSTEIN and GOLDMAN'S (1959) rubidium s6 method compares favourably with other methods. It enabled these workers to observe a significant increase in adrenal flow response to ACTtt. With it, however, an animal can only be used for one measurement.
The present article describes experiments designed to measure adrenal blood-flow changes in response to injected ACTtI, induced hypotension, and exogenous vasopressin, with the heated thermocouple of tIENsv.L, RUFF, and GOLEN~OFEN (1954) as modified by BETZ et al. (1961). This enabled continuous flow recording and the use of every animal as its own control in acute as well as chronic experiments. In addition, it promised the detection of possible relationships between adrenal blood flow and corticoid secretion, without interfering with flow.
Materials and Methods
Data were derived from 61 dogs of both sexes, weighing 15--20 kg. A. Measurement o] glandular tissue blood ]low using heated thermoeouples. Following laparotomy under chloralose, a heated thermoeouple (H~NsEL et al. 1954) as