QUANTIFICATION OF VASOACTIVE-INTESTINAL-PEPTIDE IMMUNOREACTIVITY IN THE ANTERIOR-PITUITARY GLANDS OF INTACT MALE AND FEMALE, OVARIECTOMIZED, AND ESTRADIOL BENZOATE-TREATED RATS
serotonin; expression; Endocrinology & Metabolism; estrogen; release; polypeptide; vip; hypothalamus; antisera; passive-immunization; prolactin secretion
There are considerable data suggesting that vasoactive intestinal peptide (VIP) is involved in the regulation of PRL secretion; however, the role and cell of origin of anterior pituitary VIP remain to be determined. Immunocytochemical (ICC) studies have generally failed to detect VIP-immunoreactive (IR) cells in the pituitary of the untreated rat, although VIP-IR cells have been observed in the pituitaries of hypothyroid or estrogen-treated rats. This study was designed to examine the cellular distribution and tissue content of VIP in the anterior pituitary gland of rats under selected endocrine conditions known to alter the rates of PRL and VIP synthesis and secretion. To this end, anterior pituitary VIP and PRL content (ICC and RIA) and serum PRL levels were determined in ovariectomized (OVX) and OVX rats 3 days after treatment with 7 or 70-mu-g estradiol benzoate (EB). For comparison, pituitary VIP and PRL content (ICC and RIA) and serum PRL levels in untreated male and diestrous female rats were determined. Immunostaining for VIP was accomplished using a newly developed primary antiserum. Significant numbers of VIP-IR cells per 5-mu-m section were found in the anterior pituitary glands of all animals examined (275 +/- 33 in diestrous to 481 +/- 103 cells in male rats). VIP was not colocalized with PRL in any of the pituitaries regardless of steroid treatment or sex. Furthermore, the number of VIP-IR cells per pituitary gland was not significantly correlated with sex or EB treatment. Treatment with 70-mu-g, but not 7-mu-g, EB significantly increased the pituitary content of VIP and serum PRL levels compared to those after ovariectomy. However, both EB treatments resulted in a significant increase in pituitary PRL content compared to that in untreated OVX rats. Pituitaries from male rats had several-fold more VIP and less PRL content than pituitaries from diestrous rats. These data show that 1) in contrast to previous ICC studies, VIP-IR cells are readily detected in the anterior pituitary of intact male and female and OVX as well as EB-treated rats; 2) VIP is localized to cells other than lactotrophs, regardless of the steroid background; and 3) marked changes in anterior pituitary VIP content are not accompanied by changes in VIP-IR cell number.
Carrillo A J; Phelps C J
Endocrinology
1992
1992-08
Journal Article or Conference Abstract Publication
<a href="http://doi.org/10.1210/en.131.2.964" target="_blank" rel="noreferrer noopener">10.1210/en.131.2.964</a>
Comparison of inotropic and chronotropic effects of vasoactive intestinal peptide in isolated dog atria
adenylate-cyclase; anesthetized dogs; atrium; autonomic nervous system; cardiac; conscious dogs; contractile force; heart rate; heart rate; isoproterenol; neuropeptide; neuropeptides; Neurosciences & Neurology; parasympathetic; performance; polypeptide; receptor; receptors; Substance P; vip
The positive chronotropic and inotropic effects of vasoactive intestinal peptide, VIP, were studied in an isolated canine right atrial preparation, Atria were removed, maintained in a bath, and perfused with Tyrode's solution. Contractile force and atrial depolarization were measured, VIP (18.8-600 pmol) was injected into a cannulated sinoatrial nodal artery and dose response curves were obtained. The mean EC(50) was similar for the inotropic and the chronotropic responses (136 and 144 pmol, respectively). Time courses of the onset and of recovery from the responses were measured. Times for onset of VIP effects were similar but, once the effect was initiated, rate of development of the response and recovery time from the responses were dose dependent, The increases in atrial rate lasted two to four times longer than did the increases in contractile force. Recovery from the chronotropic and inotropic responses to VIP differ, suggesting that the intracellular responses are coupled differently to the receptors. The responses to VIP were compared to those of 100 pmol isoproterenol, another positive chronotropic and inotropic agent. Isoproterenol was a slightly more potent chronotropic and inotropic agent than VIP. Desensitization of the responses was determined. Repeated exposures to VIP decreased the chronotropic response but not the inotropic response to VIP. There was no significant decrease in responsiveness to isoproterenol.
Wallick D W; Stuesse S L
Journal of the Autonomic Nervous System
1996
1996-12
Journal Article
<a href="http://doi.org/10.1016/s0165-1838(96)00091-4" target="_blank" rel="noreferrer noopener">10.1016/s0165-1838(96)00091-4</a>