Thirty-four-week-old laying hens received injections of recombinant chicken leptin to assess the role of leptin in avian ovarian function. In the first experiment, the hens (n = 60) were divided into three groups: (i) fed ad libitum; (ii) fasted; and (iii) fasted + leptin. Hens were fasted for 5 days and those treated with leptin received 250 g leptin kg

Thirty-four-week-old laying hens received injections of recombinant chicken leptin to assess the role of leptin in avian ovarian function. In the first experiment, the hens (n = 60) were divided into three groups: (i) fed ad libitum; (ii) fasted; and (iii) fasted + leptin. Hens were fasted for 5 days and those treated with leptin received 250 g leptin kg −1 body weight twice a day, i.p. In the second experiment, the hens (n = 72) were divided into four groups: (i) fed ad libitum; (ii) fasted; (iii) fasted + leptin given only during fasting (5 days); or (iv) fasted and leptin given during both fasting and 5 days of re-feeding (10 days). LH was measured in blood plasma, and progesterone and oestradiol were measured in blood plasma and the ovary by radioimmunoassay. Apoptosis was examined in the walls of the three largest yellow hierarchical follicles (F3-F1; F3 < F2 < F1; 25-35 mm) by the TdT-mediated dUTP nick-end labelling method. Results showed that the injections of leptin during fasting: (i) delayed cessation of egg laying; (ii) attenuated regression of yellow hierarchical follicles; (iii) altered ovarian steroidogenesis; and (iv) abolished the fasting-induced apoptosis in the wall of F3-F1 follicles during the first 2 days of fasting and partially attenuated apoptosis after 5 days of fasting. Prolongation of leptin injections into the re-feeding period considerably delayed the restoration of the ovary. Expression of leptin receptor in laying hens was determined by RT-PCR. The highest expression of leptin receptor was observed in the hypothalamus. Lower receptor mRNA expression was found in the hypophysis, whereas the lowest expression was observed in the ovary. Within the ovary, a relatively high expression of leptin receptor was found in the stroma with cortical follicles < 1 mm, the wall of white (1-8 mm) and small yellow follicles (> 8-12 mm), and the granulosa layer of F3 follicles. The expression of leptin receptor in the granulosa layer of F2 and F1 follicles was barely detectable. This was in contrast to a much higher expression of leptin receptor maintained in the theca layer of F3-F1 follicles. The present results indicate that in chickens leptin might be involved in the adaptation to starvation due to attenuation of follicular apoptosis. The presence of leptin receptors in the ovary indicates the possibility of a peripheral effect of the hormone.

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Wdb 2j9.m and 1 tabkReceiwd~rpnbliratia Mq 16, 1998 s-ryIn a hying hen, histamine was found to be present in all compartments of the ovary, i.e. stroma with follicles < 1 xnm, small white (14mm), large white (Mmrn), atretic white, yellow preovulatory (8-35mm) and postovulatory follicles. Stroma containing non-yotky follides exhibited the highest histamine concentration (6080 f 331 ng/g wet wt. tissue) which differed significantly (P < 0.01) from histamine levels observed in all examined classes of ovarian follicles. High histamine concentration was found in smd, large and atretic white follicles as well as in older postovulatory follicles whereas low levels of histamine contained yellow preovulatory and younger postovulatory follicles. Population of yolky white follicles presented significant (P < 0.01) differences in histamhe level among small (4280 & 333), atretic (2940 f 193) and large (2010 f 1 lOn$g) follicles. Within hierarchy of yellow preovulatory (F,-F,) follicles initial decrease in histamine concentration, from 859.3 f 51.5 ng/g in F, follicle to 363.9 f 28.3 ng/g in F, follicle, was followed by the increase as follicle matured, reachmg the hghest level in F, follicle (71 1.4 f 35.9 ng/& In postovulatory (P,-PJ follicles histamine concentration gradually increased as they were getting older, from 604.3 k 49.3 ng/g in P1 follicle to 2253 f 197 ng/g in P, follicle. Determination of histamine in rehtion to ovulation revealed significant (P < 0.01) difference both in histamine concentration and content between the largest preovulatory F, follicle and the largest postovulatory PI follicle, being 0.5 h before and 0.5 h after ovulation, respectively. It is suggested that in chicken, ovarian histamine may play a role in the fdticular development and/or the ovulatory process.

Tlus study was undertaken to determine histamine concentration in chicken oviductal parts (infundibulum, magnum, isthmus and shell gland) in relation to the egg location within the oviduct and ovulation.The experiment was performed on Hisex Brown laying hens with regular sequences of at least four eggs.Ovulation occurred within 5-15 min of oviposition of the previous egg in the series. Histamine was determined spectrofluorometrically in the following stages of the egg-laying cycle: during c2 oviposition; 0.5 h, 6.5 h, 12.5 h and 18.5 h after c2 oviposition; and during cg oviposition. Irrespective of the egg formation stage histamine concentration in the examined oviductal parts was arranged in the following order: infundibulum > magnum > isthmus > shell gland. During the egg-laying cycle hstamine concentration significantly changed. During oviposition, i.e. just before ovulation of the next egg in the series, histamine concentration significantly increased in the infundibulum while 6.5 h after oviposition, i.e. about 1.5 h of the egg stay in the shell gland, there was a significant increase in histamine concentration both in the infundibulum and the shell gland. In the magnum hstamine concentration was elevated when the ovum entered the segment, i.e. 0.5 h after oviposition. There were no changes in hstamine concentration in the isthmus. It is suggested that histamine participates in the local events taking place in the hen oviduct during the egg formation cycle.