Growth and differentiation of transplanted rat embryos in intact, diabetic and hypophysectomized hosts: comparison with their growth in situ.
The objectives of this investigation were to evaluate the suitability of a transplant system for studying the endocrine control of growth and differentiation in rat embryonic/fetal tissues, and to gain information on the development of their hormone dependence. Whole 10-day-old rat embryos were transplanted under the kidney capsule of intact, hypophysectomized (Hx) or diabetic (Db) juvenile syngeneic female hosts, and grown there for 3, 6, 9 or 12 days. The wet weight, DNA and protein content of the transplants and of age-matched in situ embryos/fetuses were measured to assess their growth. The transplants in intact hosts increased more than 300-fold in all parameters during 12 days of incubation. However, this increase was only about 4% of the in situ growth. The severe impairment in growth occurred mainly during the first 3-day period when the transplants grew only 5% as much as the in situ embryos. Between days 13 and 22 of gestational age, the increment in transplant growth was 70% of that occurring in situ. Tissue differentiation of the transplants in intact hosts was essentially normal, although they grew as teratomas. Growth and differentiation of transplants in Db and Hx hosts were delayed or inhibited. This inhibition occurred as early as day 3 after transplantation and was corrected by appropriate hormone replacement therapy of the hosts. We conclude that rat embryos/fetuses develop a dependence on a growth hormone-dependent factor (possibly somatomedin) and/or insulin for growth before day 13 of development. This transplant system will be useful for studying other aspects of the control of growth and differentiation of rat embryos/fetuses between days 10 and 22 of gestation.
Department of Physiology-Anatomy, University of California, Berkeley.
L
L
Liu
S M
SM
Russell
C S
CS
Nicoll
D000818:Animals; D004624:Embryo Transfer; D005314:Embryonic and Fetal Development; D005260:Female; D007016:Hypophysectomy; D011247:Pregnancy; D011254:Pregnancy in Diabetics; D051381:Rats; D011919:Rats, Inbred Strains