Contamination of prolactin preparations by antidiuretic hormone and oxytocin

Abstract

Since impurities consisting of neurohypophysical hormones in prolactin powder may be responsible for the vascular and renal effects attributed to prolactin, rat (NIH-RP-1), ovine (NIH-P-S-10, S-12), and bovine (NIH-P-B4) prolactin preparations were examined for their content of ADH and oxytocin by rat antidiuresis, milk-ejection, and blood pressure assays. Activities were identified as due to ADH or oxytocin by incubation of prolactin solutions with antisera against ADH, oxytocin, and prolactin, or with pregnancy plasma. The ADH content of rat, ovine (P-S-10, P-S-12) and bovine prolactin was found to be 104.5 +/- 7.1 (means +/- SE), 2.5 +/- 0.2, 1.6 +/- 0.1, and 1.6 +/- 0.5 mU/mg powder, respectively; the corresponding values for oxytocin content were 155.3 +/- 3.5, 1.2 +/- 0.1, 0.5 +/- 0.1, and 1.2 +/- 0.01 mU/mg powder, respectively. Because antidiuretic, milk-ejection, and blood pressure activities of the various prolactins were eliminated after incubation with antisera against ADH and oxytocin, or with pregnancy plasma, but not with prolactin antisera, it is concluded that the reported vascular and renal prolactin effects are attributable to ADH contamination of the prolactin preparation rather than to the prolactin molecule itself. These findings have implications for renal and vascular prolactin research.

The dipsogenic activity of prolactin in male and female rats.

“…Many of the confusing results concerning the renal actions of prolactin may have been due to vasopressin present as contaminant in the NIH preparation of ovine prolactin (Vorherr, Vorherr & Solomon, 1978;Cary, Johanson & Seif, 1977 ACTIVITY OF PROLACTIN Wilson (1976), it contains only 2-5 ng vasopressin/mg prolactin compared with 20 ng/mg prolactin in the NIH preparation. Vasopressin, even if it is present as contaminant, should prove to be less of a problem in studies on drinking than in renal physiology since its dipsogenic activity in the rat, if any, seems to be slightly depressive (Fitzsimons, 1979).…”

“…Many of the confusing results concerning the renal actions of prolactin may have been due to vasopressin present as contaminant in the NIH preparation of ovine prolactin (Vorherr, Vorherr & Solomon, 1978;Cary, Johanson & Seif, 1977). It was for this reason that the Sigma preparation was chosen since, according to Keeler & * * DIPSOGENIC ACTIVITY OF PROLACTIN Wilson (1976), it contains only 2-5 ng vasopressin/mg prolactin compared with 20 ng/mg prolactin in the NIH preparation.…”

The Effect of Hemorrhage and Hypertonic Saline upon Plasma Oxytocin and Arginine Vasopressin in Conscious Dogs*

“…However, careful studies in man of the milk-ejecting or uterine responses to iv infusions of hypertonic saline have yielded conflicting results, possibly related in part to the lesser intensity of the osmotic stimulus (4)(5)(6)(7). A major shortcoming of such studies is that AVP possesses substantial intrinsic activity in either milk ejection or uterotonic assays making it difficult to determine with certainty whether or not oxytocin (OT) was actually released (8). We have examined the specificity of two pathways for AVP release, employing sensitive and highly specific RIA procedures to determine plasma levels of AVP and OT after either hemorrhage or iv infusion of hypertonic saline in trained conscious dogs.…”

Effect of prolactin on urinary excretion and renal haemodynamics in conscious rats.

“…Some prolactin preparations (produced mainly by the U.S. National Institute of Health) are contaminated with vasopressin (Vorherr, Vorherr & Solomon, 1977;Keeler & Wilson, 1976). However, the Sigma prolactin used in the present study contains very little vasopressin (2-5 ng vasopressin/mg prolactin; Keeler & Wilson, 1976), and this cannot account for its antidiuretic activity (Miller & Van Gemert, 1976).…”