The pars distalis of the pituitary as a source of liver growth stimulating factors during liver regeneration

Plasma and pituitary extracts from hepatectomized mice as well as pure growth hormone, stimulate DNA synthesis in hepatocyte population of adult intact mouse liver. This effect is not observed with plasma and pituitary extracts from intact or sham operated mice. The corresponding effects on the litoral cell population of the liver follow the same pattern, but the results are not so clearcut as in the hepatocyte population. The possibility that growth hormone, released by STH cells of the pituitary, is one of the factors responsible for the stimulating effect of plasma during liver regeneration, is discussed on the basis of the present results and of those already reported in the literature.Facultad de Ciencias Médica

Growth hormone release after hepatectomy

El plasma de ratones hepatectomizados, recogido a la medianoche del segundo dia de la regeneracion, estimula, al igual que la hormona de crecimiento pura, la sintesis de ADN de los hepatocitos y celulas litorales del higado del raton adulto intacto. Este efecto no se observa con el plasma de ratones intactos sacrificados a medianoche ni con solucion fisiologica. Se sugiere que el factor estimulante del plasma de ratones hepatectomizados en hormona de crecimiento.Facultad de Ciencias Médica

Circadian variations of DNA synthesis, mitotic activity, and cell size of hepatocyte population in young immature male mouse growing liver

Circadian variations in DNA synthesis after tritiated thymidine and autoradiography, mitotic activity with the Colcemid method, and cell size, represented inversely by the number of cells per microscopic field, are reported for the hepatocyte population of the young immature growing liver of the male mouse. The peak of DNA synthesis is at 04:00 hours and that of mitotic activity at 12:00 hours. The 8-hour interval between the two peaks is considered, in agreement with other authors, a good estimation of the lag period between DNA synthesis and the initiation of mitotic activity. The minimum cell number per microscopic field, which is considered to correspond to the maximum cell size, coincides with the starting of the circadian mitotic wave. The significance of this coincidence and the relationships of the circadian curves of the parameters controlled with the feeding pattern and food consummatory curve of standardized mice, are discussed.Facultad de Ciencias Médica