Identification of immunoreactive somatostatin in the rat harderian gland: regulation of its content by growth hormone, beta-adrenergic agonists and calcium channel blockers.
Immunoreactive somatostatin (IRS) was identified in the male rat Harderian gland (HG) by radioimmunoassay. Tissue was extracted and a displacement curve performed; there were no significant differences between values obtained with serial dilutions of extracted tissue and those from purified somatostatin standard used in the radioimmunoassay. Basal values of HG-IRS were found to be in the nanomolar range (10.8 +/- 3.5 ng IRS/mg protein). Hypophysectomy did not change the HG-IRS but, in vivo growth hormone (GH) treatment led to a dramatic increase (6-7-fold) in the levels of IRS in the HG. Isoproterenol, a beta-adrenergic agonist, when administered in vivo significantly decreased the HG-IRS content. The effect of two different calcium channel blockers on the isoproterenol-induced decrease of HG-IRS was studied; no changes were observed with nifedipine but verapamil, injected one hour after isoproterenol administration, prevented the drop in HG-IRS levels. These data demonstrate the existence of IRS in a new location, the rat Harderian gland, and support a classical endocrine regulation for its tissue concentration.
D000818:Animals; D013006:Growth Hormone / Q000494:pharmacology*; D006243:Harderian Gland / Q000187:drug effects / Q000378:metabolism*; D007016:Hypophysectomy; D007545:Isoproterenol / Q000494:pharmacology*; D007765:Lacrimal Apparatus / Q000378:metabolism*; D008297:Male; D009543:Nifedipine / Q000494:pharmacology*; D011863:Radioimmunoassay / Q000379:methods; D051381:Rats; D012016:Reference Values; D013004:Somatostatin / Q000276:immunology / Q000378:metabolism*; D014700:Verapamil / Q000494:pharmacology*
D013004:Somatostatin; D013006:Growth Hormone; D014700:Verapamil; D009543:Nifedipine; D007545:Isoproterenol