Frequency of luteinizing hormone pulses and circulating 17β-oestradiol concentration in cows is related to concentration of progesterone in circulation when the progesterone comes from either an endogenous or exogenous source

E. G. Bergfeld, F. N. Kojima, M. E. Wehrman, A. S. Cupp, K. E. Peters, V. Mariscal, T. Sanchez, R. J. Kittok, M. Garcia-Winder, J. E. Kinder

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Abstract

The present study was designed to test whether progesterone from exogenous and endogenous sources modulates the frequency of luteinizing hormone (LH) pulses in a differential fashion. Our working hypotheses were: (1) the frequency of secretion of LH pulses and concentration of 17β-oestradiol in circulation would be directly related to circulating concentration of progesterone; (2) progesterone from an exogenous source would have a different effect on frequency of LH pulses and circulating concentration of 17β-oestradiol than progesterone from an endogenous source. Cows were treated with graded doses of PGF or progesterone to result in varying concentrations of progesterone in circulation from endogenous and exogenous sources. Treatment with PGF resulted in concentrations of circulating progesterone among animals in this group that ranged from 0.5 to 10.9 ng ml-1 of plasma. Treatment with progesterone resulted in circulating concentrations of progesterone among animals in this group that ranged from 0.8 to 11.8 ng ml-1 of plasma. Concentrations of progesterone in circulation and frequency of LH pulses were negatively correlated (r = -0.59) in cows with functional corpora lutea and in cows treated with progesterone without corpora lutea (r = -0.62). The frequency of LH pulses had the same relationship to the varying concentrations of progesterone in both treatment groups. Cows with higher progesterone levels had fewer LH pulses and cows with lower progesterone had a greater frequency of LH pulses. Mean circulating concentrations of 17β-oestradiol also had the same relationship with varying concentrations of progesterone in both treatment groups. Cows with higher progesterone levels had lower 17β-oestradiol and cows with lower progesterone had higher 17β-oestradiol levels. The results indicate that there is a direct relationship between circulating concentration of progesterone, frequency of LH pulses and circulating concentration of 17β-oestradiol. In addition, progesterone modulates the frequency of release of LH pulses from the pituitary and circulating concentration of 17β-oestradiol in a similar fashion when coming from either an endogenous or exogenous source.

Original languageEnglish (US)
Pages (from-to)257-265
Number of pages9
JournalAnimal Reproduction Science
Volume37
Issue number3-4
DOIs
Publication statusPublished - Feb 1995

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Keywords

  • Cattle - endocrinology
  • Luteinizing hormone
  • Oestradiol
  • Progesterone

ASJC Scopus subject areas

  • Food Animals
  • Animal Science and Zoology
  • Endocrinology

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