The content of beta-endorphin-like immunoreactivity in porcine corpus luteum and the potential roles of progesterone, oxytocin and prolactin in the regulation of beta-endorphin release from luteal cells in vitro.
The amount of beta-endorphin-like immunoreactivity (beta-END-LI) in porcine corpora lutea from several stages of the oestrous cycle and the effects of progesterone, oxytocin, and prolactin on beta-END-LI secretion in vitro by luteal cells were studied. Porcine corpora lutea obtained on days 1-5, 6-10, 11-13, 14-18, and 19-21 of the cycle were used to prepare extracts for beta-END-LI determination. Additionally, corpora lutea from days 11-13 and 14-18 were enzymatically dissociated and isolated luteal cells were used for further study of beta-endorphin secretion in vitro. Cells were cultured in serum-free defined M 199 medium (106 cells/ml) at 37 degrees C under 5% CO2 in air, for 12 h. The influences of the following factors on beta-END-LI secretion by luteal cells were tested: progesterone (10-9, 10-7 and 10-5 M), oxytocin (0.01, 0.1, 1 and 10 ng/ml), and prolactin (0.1, 1, 10 and 100 ng/ml). The beta-END-LI contents in extracts and media were measured by radioimmunoassay. The tissue concentration of beta-END-LI was lowest on days 1-5 of the cycle (0.35 +/- 0.03 ng/g wet tissue). Subsequently, it constantly increased to the highest value on days 14-18 (16.58 +/- 0.52 ng/g wet tissue) and on days 19-21 it declined (11.10 +/- 0.52 ng/g wet tissue). Progesterone at a low dose (10-9 M) resulted in significant (p < 0.05) increases and decreases in beta-END-LI secretion by luteal cells from days 11-13 and 14-18, respectively. Higher doses of progesterone (10-7 and 10-5 M) had no effect on beta-END-LI release, compared with the control group. All dose-levels of oxytocin used decreased beta-END-LI secretion by luteal cells on days 11-13 and 14-18 of the cycle. Prolactin at doses of 0.1 and 1 ng/ml on days 11-13, and all doses tested on days 14-18 resulted in decreases in beta-END-LI release from luteal cells. These results document evident changes in beta-END-LI content in the pig corpus luteum during its development and indicate the potential roles of progesterone, oxytocin, and prolactin in luteal cell secretion of beta-END-LI.
Przala
J
J
Department of Animal Physiology, University of Warmia and Mazury in Olsztyn, Olsztyn, Poland. jadwigap@art.olsztyn.pl
Kaminski
T
T
Okrasa
S
S
Siawrys
G
G
Bogacka
I
I
D000818:Animals; D002478:Cells, Cultured; D003338:Corpus Luteum / Q000166:cytology; D005260:Female; D008184:Luteal Cells / Q000187:drug effects / Q000378:metabolism*; D010121:Oxytocin / Q000008:administration & dosage / Q000494:pharmacology* / Q000502:physiology; D011374:Progesterone / Q000008:administration & dosage / Q000494:pharmacology* / Q000502:physiology; D011388:Prolactin / Q000008:administration & dosage / Q000494:pharmacology* / Q000502:physiology; D013552:Swine / Q000502:physiology*; D013997:Time Factors; D001615:beta-Endorphin / Q000378:metabolism*
D011374:Progesterone; D010121:Oxytocin; D001615:beta-Endorphin; D011388:Prolactin