Other effects of LH

The development of ovarian cells and Leydig cells is also under the influence of LH [3,90], In the testis the development of the Leydig cells is completed during puberty and no further development occurs. In the ovary, the development of LH responsive cells is cyclic during the active period of reproduction. In both gonads there are still many uncertainties about the exact origin of the steroid producing cells and about the final steps that ultimately lead to the mature cells. 

Hypophysectomy leads to an 80% decrease in interstitial fluid volume which is returned to normal by injection of hCG. The mediator of this effect is either produced directly by the Leydig cells in response to LH or originates in other cell types, e.g., macrophages or Sertoli cells in response to Leydig cell factors. The increases in interstitial fluid volume may be caused by mechanisms similar to those inducing oedema in acute inflammation. After hCG treatment, polymorphonuclear leukocytes (PMNs) accumulate in testicular blood vessels prior to the increases in the interstitial fluid volume and then migrate into the interstitial spaces 4 and 8 h after injection this invasion by PMNs may be caused by the release of a chemotactic agent [97]. 

In the ovary the ovulatory surge of LH increases blood flow [98]. This is accompanied by an increase in vascular permeability in the follicles resulting in oedema which persists through the time of follicle rupture and ovulation. The effect of LH can be mimicked by histamine but not by FSH or serotonin. Leukocytes accumulate in Graafian follicles near the time of ovulation and fibroblasts migrate from the theca layer to the stratum granulosum. 

After one injection of hCG to rats, testosterone production is maximally stimulated within 2 h, whereas steroidogenic lesions develop between 12 and 24 h. The effect of hCG on prostaglandin production is different within 2 h no effect can be demonstrated, whereas between 12 and 24 h, PGF2a and PGE2 levels rise more than 5-fold [17]. 

In Leydig cells from mature rats isolated 10 days after two injections of hCG (administered at day 0 and day 7) LH receptors are down regulated and adenylate cyclase is desensitized , however, the LH-dependent steroidogenic capacity is increased [104]. 

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