Cellular Growth in the Organs of the Hypopituitary Dwarf Mouse

To investigate the role of the anterior pituitary gland in cellular growth, genetic hypopituitary dwarf mice were compared to littler mate controls. Total organ weight, DNA, RNA and protein were determined in 12 organs (brain, liver, lung, kidney, heart, skeletal muscle, tongue, submaxillary gland, pancreas, stomach, spleen and thymus). No biochemical differences were found between organs of homozygous and heterozygous normal animals. However, all organs from homozygous dwarf animals contained less DNA from 15 through 51 days of age than organs from normal litter mates. This is due at least in part to a premature cessation of cell division. All dwarf organs failed to incorporate 14Cthymidine into DNA after the 26th day, whereasorgans of normal animals continued to incorporate beyond 51 days. Protein/DNA ratios were normal in certain organs (lung, liver, salivary gland, pancreas, stomach, spleen and thymus) and reduced in others (brain, kidney and muscular tissues). Thus, after 15 days all organs of dwarf animals contained fewer cells, and by 26 days no further cell division could be demonstrated. Concomitantly, individual cell size was reduced in certain organs. These data demonstrate that the number of cells in all organs, the time when cell division ceases, and the size of individual cells in certain organs depend either directly or indirectly on anterior pituitary function. (Endocrinology83: 544, 1968)