Seasonal variations in testicular LH, FSH, and PRL receptors; in vitro testosterone production; and serum testosterone concentration in adult male vizcacha (Lagostomus maximus maximus).
Seasonal changes in the reproductive activity of the adult male vizcacha (Lagostomus maximus maximus), a South American rodent, were investigated. Monthly, for 1 year, the animals were captured during the night near their burrows in the vicinity of San Luis, Argentina. The animals were killed, and samples of blood and the testes were collected. The testosterone serum levels were determined and the testicular tissue was used for biochemical and structural studies. Significant changes associated with seasonal cycles were found. In July-August (winter in South America), a short hibernal period of sexual quiescence, decline in testicular volume, and a significant decrease in serum testosterone were observed. The in vitro testosterone production and testicular LH, FSH, and PRL receptors revealed a significant decrease during this period. During September-November (spring season), recovery was observed, with a significant increase in gonadal activity during April-May (autumn season). During this season, the gonadal volume was increased, the serum testosterone and the in vitro stimulation of testosterone production by hCG (as well as the basal levels) also revealed a significant increase. Correspondingly, the concentration of testicular LH, FSH, and PRL receptors was elevated. These results indicate an increase in parameters related to testicular function. A gradual reduction in the testicular activity was observed in June-July (early winter). Our findings indicate that the male adult vizcacha, under natural conditions, exhibits characteristics of an annual reproductive cycle.
Area de Farmacología, Universidad Nacional de San Luis, Argentina.
L B
LB
Fuentes
J C
JC
Calvo
E H
EH
Charreau
J A
JA
Guzmán
D000818:Animals; D006461:Hemolysis; D007985:Leydig Cells / Q000502:physiology; D008297:Male; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011962:Receptors, FSH / Q000378:metabolism; D011974:Receptors, LH / Q000378:metabolism; D011981:Receptors, Prolactin / Q000378:metabolism; D012377:Rodentia / Q000502:physiology*; D012621:Seasons; D013737:Testis / Q000033:anatomy & histology / Q000378:metabolism*; D013739:Testosterone / Q000096:biosynthesis / Q000097:blood*
D011956:Receptors, Cell Surface; D011962:Receptors, FSH; D011974:Receptors, LH; D011981:Receptors, Prolactin; D013739:Testosterone