RESUMEN
Changes in the specific activities and distribution of lactate dehydrogenase (LDH) isoenzymes have been studied in the oviduct of intact, ovariectomized and ovariectomized-hormone treated rats. Total LDH and M-subunits were higher in the oviduct during estrus compared to early diestrus phase. Ovariectomy lowered the total activity as well as the proportion of H and M-subunits of LDH, with a total loss of LDH. Treatment of ovariectomized rats with progesterone (2 mg/100 g. body wt/rat/day) and estradiol-17 beta (0.5 microgram/100 g body wt/rat/day) for 7 consecutive days induced marked augmentations in the total activities of this oviducal enzyme. Further, there was a shift in the isoenzyme patterns towards M-type, especially LDH5. Prolactin (400 microgram/100 g body wt/rat/day) depressed the total LDH activity and the distribution of isoenzymes. While LDH4 and LDH5 were very low, LDH1--LDH3, were inclusive, were absent in the oviduct of prolactin-treated group. None of the hormonal replacements could stimulate the LDH4 - subunit. The significance of these changes has been discussed in relation to metabolic activities in the tissue and hormonal influences.