Effects of elevated prolactin and its normalization on thyroid hormone, cardiac beta-adrenoreceptor number and beta-adrenergic responsiveness.
Subcutaneous inoculation of the prolactin secreting MtTW15 adenoma in male Wistar Furth rats for 4 weeks produced a significant increase in serum prolactin and a corresponding decrease in peripheral beta-adrenergic responsiveness. Both the isoproterenol induced drink and heart rate responses used to assess the beta-adrenergic responsiveness were significantly reduced in the hyperprolactinemic rat. Serum T3 and T4 levels were measured as was cardiac beta-adrenergic receptor number to ascertain if an alteration of thyroid hormone and a resultant decrease in beta-adrenergic receptor number was responsible for the attenuated beta-adrenergic responsiveness. Serum T4 was significantly reduced in the hyperprolactinemic group (1.9 +/- 0.3 microgram%) as compared to the control group (6.4 +/- 0.l5 microgram%). However there was no significant difference in serum T3 or in cardiac beta-adrenergic receptor number between the two groups. Removal of the MtTW15 adenoma resulted in a normalization of serum prolactin, T4, and in the responsiveness of the peripheral beta-adrenergic system within 4-6 weeks. These results indicate that the attenuated beta-adrenergic responsiveness associated with hyperprolactinemia is reversible and not dependent on a reduction in beta-adrenergic receptor number.
D000236:Adenoma / Q000378:metabolism; D000818:Animals; D004326:Drinking / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D009368:Neoplasm Transplantation; D010911:Pituitary Neoplasms / Q000378:metabolism; D011388:Prolactin / Q000097:blood*; D051381:Rats; D011920:Rats, Inbred WF; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D013894:Thirst / Q000502:physiology*; D013963:Thyroid Hormones / Q000097:blood*; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
D011943:Receptors, Adrenergic, beta; D013963:Thyroid Hormones; D014284:Triiodothyronine; D011388:Prolactin; D007545:Isoproterenol; D013974:Thyroxine