Abstracts 403

(P < 0.001 for values compared at 24 h and at 48 h). Three bridge technique. The density of staining was greatly in- treatment groups (30mg PGFs, s.c., n = 6; 7OOpg ICI creased in the theta layer but not in the granulosa layer 79939i.m., n = 5; 8OOpg ICI 80996 i.m., n = 16) were by treatment with 10 pg/ml of LH or PGE,. Indomethacin sampled 3-hourly around induced oestrus to assess para- (1 mg/ml) did not appear to affect the density of staining meters of the preovulatory LH release, and results com- due to LH. Levels of CAMP (pmole/follicle) were as pared with those of animals sampled around normal oestrus. Mean times from onset of oest&s to the LH peak for the

follows: control, 2.4; LH (lOpg/ml), 162.0; PGE, (lOpg/ ml), 9.0; LH plus indomethacin (1 mg/ml), 3.6; LH plus

4 arouns were 3.0,5.4.3.5 and 4.2 h resoectivelv. while neak concentrations (ng/ml) of LH were 38.3 f 4.5, 36.0 i 6.9,

eicosatetraynoic acid (100 pg/ml), > 100 ; indomethacin alone(1 mg/ml), 6.0; eicosatetraynoic acid alone (100 pg/ml),

3l.Ok3.6 and 37.7 k2.8 respectively. These results suggest 4.8. Both LH and PGE, stimulated CAMP but the effect of that an estimate of progesterone concentration 48 h after LH was much greater. Indomethacin but not eicosatetray- injection reflects the efficacy of a particular luteolytic noic acid prevented stimulation of CAMP by LH, a regimen and that there are no abnormal changes when difference of effect which may be dose related. The data oestrus and ovulation are induced by any of these 3 are consistent with the hypothesis that PGE, is involved in prosmglandin treatments. the action of LH on the follicle.

449. Endocrine changes in fresian heifers during luteolysis and oestrous synchronization with I.C.I. 80,996, a synthetic analogue of prostaglandm F,, COOPER, M. J., DoB~~N, H. and Fuaa, B. J. A., Imperial Chemical Industries Limited, Pharmaceuti- cals Division, Alderley Park, Macclesfield, Cheshire, England

The exploitation of prostaglandin (PG)-induced luteolysis for the synchronization of oestrus in cattle depends on the availability of a PG analogue which causes luteolysis on parenteral administration in very low doses and a procedure whereby it can be used effectively without knowledge of previous oestrus dates. This paper describes the response to such an analogue, I.C.I. 80,996, given in a way (2 doses, 11 days apart) that satisfies the latter requirement. A dose of 500 pg I.C.I. 80,996 administered i.m. to 7 heifers in the luteal phase of the oestrous cycle caused a marked fall in plasma progesterone with 6 h of treatment, with basal levels reached with 24 h; oestradiol-17/l was elevated and reached peak values immediately before the LH surge which occurred 70-100 h after the injection. These endocrine changes were accompanied by luteal regression, rapid follicular develop: ment and ovulation as judged by rectal palpation. Oestrous mucus was seen in the vagina 48-96 h post-treatment. A further injection of 500 pg I.C.I. 80,996 11 days after the first treatment produced an identical series of endocrine and gross morphological changes although the return to oestrus and ovulation was more rapid and precise. The magnitude and time-course of these changes were similar to those occurring before the onset of natural oestrus and the induced cycle was of a normal length. The administration of ICI. 80,996 in doses 11 days apart produces precise oestrous synchronization and can be used in herds without reference to the previous oestrous dates, since at the time of the second injection all animals will be in the sensitive phase of the oestrous cycle, between days 7 and 15.

450. Localization of cyclic AMP in rabbit ovarian follicles and effects of LH and PGE, BULLOCK, D. W., CLARK, M. J., AGRAWAL, R., FURTH, E. D. and STEINW, A. L., Albany Medical College, Albany, N.Y., U.S.A.

Rabbit ovarian follicles were incubated in the presence of LH or PGE,, with or without inhibitors of prostaglandin synthesis. Levels of CAMP were determined by radio- immunoassay and the nucleotide was localized in frozen sections of follicles by an immunoglobulin-peroxidase

451. Gonadotropin-sensitive adenylate cyclase in rat testis mitochondria SULIMOVICI, S. and LUNENFELD, B., Institute of Endocrinology, The Chaim Sheba Medical Centre, Tel Hashomer, and Department of Life Sciences, Bar-Ilan University, Ramat Gan, Israel

Adenylate cyclase activity in purified mitochondria from both immature and mature rat testes was increased when stimulated by LH, HCG or FSH. The response was found to be the same in all cases except FSH induced much higher activity in the enzyme from immature rats. The mitochondrial adenylate cyclase was solubilized (80%) with non-ionic detergent Lubrol PX and then purified by DEAE cellulose chromatography and gel filtration on Sepharose. Solubilization resulted in loss of response to gonadotropins but not to NaF. Addition of phosphatidylserine to the solubilized preparation partially restored the responsive- ness of adenylate cyclase to HCG. These findings suggest that gonadotropins activate the adenylate cyclase attached to the mitochondrial membranes and the activity of the enzyme is probably dependent on the integrity of the lipid protein complex.

13C. Sex hormones and cyclic AMP

452. Similarities between cyclic AMP and progesterone receptors in the chick oviduct KELLER, R. K., CHANDRA, T. and SCHRADER, W. T., Department of Cell Biology, Baylor College of Medicine, Houston, Texas, U.S.A.

The induction of new RNA by steroid hormones appears to require the interaction of steroid “receptors” with nuclear components. Recent evidence suggests that increases in the phosphorylationofchromosomalproteins by protein kinases may accompany these events. The cytoplasmic protein kinase of oviduct has been partially purified and character- ized. The native enzyme has a mol wt of 180,000 while the cyclic AMP (CAMP) binding regulatory subunit (CR) and the catalytic subunit(E) have mol wt of 120,000 and 50,000, respectively. This suggests that the native complex is com- posed of one regulatory and one catalytic subunit. To study the possible regulation of protein kinases by steroid hormones, we have investigated the relationship between CR and the progesterone recentor (PR) in the chick oviduct. Our results show that the two binding proteins are similar macromolecules, since they are both acidic proteins and co- elute from DEAE-cellulose (0.2 M KCl), hydroxylapatite