title: Developmental pattern and sensitivity to down-regulation of testicular LH receptors in the pig.
abstract: Testicular receptors for luteinizing hormone (LH) were quantified in 40 pigs between the day of birth and 22 weeks of age. The highest specific binding capacity (fmol hLH bound/mg protein) occurred at about 2--3 weeks of age which coincides with the age when the relative volume of Leydig cells is at a maximum. Significantly lower binding capacity was observed at 7 weeks of age which is the time of maximum Leydig cell regression. hCG was injected intramuscularly to immature (3000 IU, 22 days old) and adult boars (10 000 IU, 30--40 weeks old). Twentyfour h after injection the numbers of available LH receptors were reduced to 6 and 18% of control values, respectively. At this time occupied receptors were at a maximum (90% and 67% of controls, respectively). The total number of LH receptors (available + occupied) was increased 1 h after injection after which a gradual decrease was observed. Three days after hCG administration the total receptor quantities were at a minimum in both immature and adult pigs (59% and 31% of controls, respectively) and returned to control levels 5--7 days after treatment. Thus, pig LH receptors appear to be subjected both 'positive' and 'negative' regulation as previously described in the rat.
mesh_terms: D000375:Aging; D000818:Animals; D007985:Leydig Cells / Q000378:metabolism; D007986:Luteinizing Hormone / Q000378:metabolism; D008297:Male; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011974:Receptors, LH; D013552:Swine; D013737:Testis / Q000378:metabolism*
chemical_list: D011956:Receptors, Cell Surface; D011974:Receptors, LH; D007986:Luteinizing Hormone