Glycosyltransferase and UDP-galactose pyrophosphatase activities in the endometrium during oestrous cycle of the rat.

UDP-galactose: glycoprotein galactosyltransferase, CMP-sialic acid: glycoprotein sialyltransferase and UDP-galactose pyrophosphatase activities were measured in the endometrium of rat uteri during the oestrous cycle. The galactosyltransferase activity started to increase at dioestrus and reached a maximum on the afternoon of pro-estrus. The UDP-galactose pyrophosphatase activity changed in a direction opposite to that of galactosyltransferase. The sialyltransferase activity was low during metoestrus and dioestrus, but began to rise on the morning of pro-oestrus, reaching a peak on the morning of oestrus. Previously, we have shown that oestradiol administration stimulated galactosyl- and sialyltransferase and inhibited pyrophosphatase activities several-fold in the endometrium of ovariectomized rats. Progesterone prevented the oestradiol effect on the enzymes. The changes in glycosyltransferase and pyrophosphatase activities during the oestrous cycle possibly bear a direct relationship to the ovarian hormones in the rat during the normal oestrous cycle. This relationship will then be conducive to increased synthesis of glycopolymers during ovulation. Furthermore, the lag of 18 h for a maximal rise of sialyltransferase following that of galactosyltransferase is consistent with the normal sequence of glycosylation that occurs in glycoprotein secretion.

Effect of estradiol and progesterone on UDPgalactose pyrophosphatase activity in the endometrium of ovariectomized rats.

Rat endometrium was found to contain a UDPgalactose pyrophosphatase for the hydrolysis of UDPgalactose into galactose 1-phosphate and UMP. The adminstration of 17beta-estradiol to ovariectomized rats resulted in a significant decrease in the activity of the enzyme in endometrium while have little effect on that in myometrium. The response was linear with the dose of estradiol and as little as 0.07 mug per 100 g body weight produced maximum inhibition of the enzyme. Progesterone on its own had little effect on the enzyme activity but in combination with estradiol, it effectively prevented the inhibitory effect of estradiol. This inhibitory effect of estradiol on the activity of UDPgalactose pyrophosphatase may function in the regulation of glycoprotein biosynthesis in endometrium.

Comparison of the intermediary metabolism of fatty acids in denervated and dystrophic murine skeletal muscle.

Certain aspects of lipid metabolism have been examined in denervated muscle from normal mice and in dystrophic muscle from mice of the Bar Harbor strain 129. A number of parameters show no change or similar changes. For example, the utilization of palmitate-[1-14C] and palmitylcarnitine by mitochondria from denervated and dystrophic hind leg skeletal muscle showed parallel decreased in the oxidation of palmitate (30-42%) and palmitylcarnite (37-66%). A comparable study with acetylcarnitine showed a striking difference with no change evident in mitochondria from denervated muscle and 80-85% decrease in dystrophic muscle. The study of succinate dehydrogenase and the enzymes of beta-oxidation in the above mitochondrial preparation showed similar findings except for acyl CoA dehydrogenase activity (an enzyme with a regulatory role in beta-oxidation) which was significantly diminished (29%) in denervated muscle, whereas no change was observed in dystrophic muscle. The findings show a close parallel in a number of parameters but distinct differences were observed in denervated as compared with dystrophic muscle. It is unlikely that the muscular disorder in murine muscular dystrophy can be explained solely on the basis of denervation or the loss of a neural trophic factor.