The reaction of dogs to stimuli of vascular tone at various intervals after hypophysectomy

Summary

Chronic experiments were staged on hypophysectomized dogs. At various intervals following the operation (from 1–3 months to 2 years) a study was made of the blood pressure and its shifts due to the effect of adrenalin pituitrin, acute blood loss and after the action of these substances against the background of blood-letting. The blood pressure in dogs sinks appreciably after total hypophysectomy. Following partial hypophysectomy the blood pressure reduction was not as great or it even remained on the former level but became more labile. In total hypophysectomy the reaction to adrenalin was more pronounced than after partial hypophysectomy. This declined with the progress of time after the operation. The reaction of dogs to pituitrin was more marked after total hypophysectomy; no relation to the time lapse after the operation was noted. An acute blood loss caused a pronounced blood pressure reduction only in dogs subjected to total hypophysectomy during the first postoperative months; later this reaction became less marked. A more pronounced reaction occurred upon the administration of adrenalin or pituitrin to totally hypophysectomized dogs after blood-letting.