The effect of growth hormone and insulin on limb-bone rudiments of the embryonic chick cultivated in vitro

Glucose transport in osteoblast-enriched bone explants: characterization and insulin regulation

Insulin has potent effects on osteoblast function both in vivo and in vitro. In various insulin-sensitive tissues, stimulation of glucose transport and metabolism are hallmarks of insulin action, and have been postulated to play a role in insulin regulation of cellular function. However, insulin effects on glucose metabolism in osteoblast-like cells have not been demonstrated. Therefore we examined the in vitro effects of insulin on hexose uptake in an osteoblast-enriched rat bone explant preparation. Uniform 5-mm-diameter punch sections were obtained from the cartilage-free frontal portions of the calvaria of 3-day-old rats, and the periosteum was removed. The resulting sections contained a highly enriched population of osteoblast-like cells as determined by histologic criteria, elimination of calcitonin-stimulatable cAMP generation, and enhancement of PTH-stimulatable cAMP generation per microgram of DNA. Sections were incubated for 24 hr at 37 degrees C in BGJb medium and then transferred to modified glucose-free Krebs-Ringer bicarbonate buffer for 2-deoxy-D-glucose (2-DG) uptake studies. 3H-2-DG uptake was linear with time over 60 min, temperature sensitive, and inhibited by 5 mM phloridzin. Kinetic analysis of 2-DG uptake at 25 degrees C demonstrated a saturable transport mechanism with a Km of 2.2 mM, similar to that observed for 2-DG transport in other tissues. Studies of competitive inhibition by other sugars demonstrated a transport specificity for 2-DG that was comparable to that previously observed in fat and muscle cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Culture in vitro as a means of analysing the effect of maternal diabetes on embryonic development in rats

Rodents have been used by many investigators for studies of the effects that maternal diabetes during pregnancy may have on developing fetuses. In Wistar rats, the induction of mild chronic diabetes at the onset of pregnancy by alloxan or streptozotocin results in abnormalities of the nervous system and the heart, recognized in embryos at 11--13 days' gestation. Thus, early organogenesis is evidently affected in these embryos. With a method which enables rat embryos to be cultured in vitro in serum for the period of their early organogenesis, the growth and differentiation of embryos from normal and from diabetic rats can be observed in some detail. It is also possible to compare the effects of normal and of diabetic maternal serum on their development. The results reported here show that embryos from diabetic animals are more likely to be retarded or abnormal than those from non-diabetic animals when cultured in identical serum. The development of both types of embryo is more successful in diabetic than in non-diabetic serum, however, possibly because of the higher glucose content of diabetic serum. Cultures of fetal organs may also be used as test systems for the effects of diabetic maternal serum. Sacral vertebrae, some of which fail to ossify in fetuses from daibetic rats, are now being grown in media containing diabetic serum. It is planned to test the effects of insulin on these cultures.