Maire T. Buckman

Osmolar control of prolactin secretion in man.

To study the effect of changing serum osmolality on serum prolactin concentration 11 volunteers were given oral and intravenous hypotonic and hypertonic fluids. Mean serum prolactin fell to 10.5 percent of baseline after oral water loading and to 15 percent of baseline after intravenous hypotonic saline infusion. Conversely, mean prolactin rose to 417 percent of baseline after intravenous hypertonic saline administration. The correlation coefficient of simultaneously determined serum prolactin and osmolality was highly significant (P 〈 .001). Isoosmolar changes in extracellular fluid volume did not consistently affect the concentration of prolactin in the serum. Thus, prolactin may be involved in the physiologic regulation of osmolar balance and the kidney may be an important farget organ for prolaction.

Role of alpha-adrenergic blockade on alanine-induced hyperglucagonemia☆

Abstract The influence of alpha-adrenergic tone on substrate-stimulated hormone secretion has been demonstrated in the pancreatic beta cell. In the present study we have examined this event in the pancreatic alpha cell. Serum glucagon response to aminogenic stimulation with alanine was found to be significantly potentiated by concurrent phentolamine-induced alpha-adrenergic blockade. Propranalol-induced beta-adrenergic blockade did not influence aminogenic glucagon secretion. The alpha-adrenergic receptors of both the pancreatic alpha and beta cells are thus important to substrate-stimulated hormone secretion.

Effect of fasting on alanine-stimulated insulin and glucagon secretion

Abstract The effect of a 5-day fast on glucose- and alanine-stimulated insulin and glucagon secretion was examined in the dog. As predicted from investigation of other species, prolonged fasting markedly inhibited glucogenic insulin secretion. In contrast, insulin and glucagon secretion after alanine challenge were unaltered by the prolonged fast. These data support the hypothesis that the physiologic response to this amino acid with fasting may be partially responsible for the regulation of insulin secretion in this state.

The value of prolactin dynamics as a predictor of ovulation with bromocriptine in patients with polycystic ovary syndrome

Six euprolactinemic polycystic ovary syndrome (PCOS) patients were subjected to a 24-hour study with serum sampling every 30 minutes and a perphenazine stimulation test. The serum prolactin (PRL) levels were compared with those of five healthy normoprolactinemic women whose cases were evaluated in a similar fashion. In addition to evaluating the PRL secretory pattern and lactotroph response, the PCOS individuals were given dopamine agonist therapy in a graduated dosage schedule, increasing each month, over a 3-month interval. The PCOS patients exhibited parallel but lower PRL levels than the control subjects during the late evening and early morning hours (P less than 0.0001) and were less responsive to perphenazine at the 6-hour sampling (P less than 0.05). Only one PCOS individual had suggestive evidence of ovulation over the 15 cycles the group was monitored. Therefore, we conclude that euprolactinemic PCOS patients who are nocturnal hyposecretors of PRL and who hyporespond to a perphenazine stimulation test are not likely to ovulate on bromocriptine in the dosages used in this study.