Concentraciones plasmáticas de las hormonas esteroides y de LH en respuesta a la administración de prostaglandinas en ovejas Bergamacia

progesterone (p4), estradiol (e2) and luteinizing hormone (lh) concentrations during synchronized estrous cycle using prostaglandin (pgf2 ) in sheep were studied. ewes were randomly divided in two groups (n=7/group): t1 synchronized with two injections of pg, given 7 days apart, and t2, female showing natural estrous. blood samples were collected from one day before pg and during experiment for steroidal determination. for profile of luteinizing hormone (lh) pulses, blood samples were collected at 30-min intervals for a period of 8h on days one, six and 12. hormonal concentrations were determined by radioimmunoassay. mean concentrations of p4 (p<0.001) were different between groups, days (p<0.0001) and interaction treatment x day. in t1 and t2, the animals showed increases in p4 plasma concentrations on day 11 (3.01 ± 0.48 ng/ml) and day eight (4.49 ± 0.45 ng/ml), respectively. mean plasma lh concentration was different on day 12 (p<0.05) among t1 (2.45 ± 0.70 ng/ml) and t2 (0.95 ± 0.17 ng/ml). the lh pulse amplitude on day six (p<0.01) differed between the two groups, for t1 was 2.29 ± 0.33 ng/ml and t2 was 1.49 ± 0.34. differences in lh pulse frequency on day six (p<0.05) were observed. these data suggest that use of pgf2 alters plasma concentrations of p4 and it could reduce lh pulse frequency.