Department of Physiology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72201, U.S.A.
(Received 27 April 1976)
The administration of various prolactin preparations to mammals has been shown to decrease urine flow (Lockett & Nail, 1965; Horrobin, Lloyd, Lipton, Burstyn, Durkin & Muiruri, 1971) and suppress diuresis induced by expansion of the extracellular fluid volume with saline (Lucci, Bengele & Solomon, 1975). It was assumed in these studies that the antidiuresis was due to prolactin. Antidiuretic hormone (ADH), however, may be present in certain ovine extracts from the pituitary which also could lead to a decrease in urine flow and suppression of diuresis (Rabkin, Swann, Shapiro & Isaacson, 1974). Consequently, we examined the possibility that ADH was present in an ovine prolactin preparation (NIH-P-S10) in quantities sufficient to cause antidiuresis.
Experiments were performed on male, Sprague–Dawley rats anaesthetized with pentobarbitone. The rats were placed in the ventral position on