Comparison between K+-induced and LHRH-induced gonadotropin secretion in vitro

Judith L Turgeon, D. W. Waring

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19 Citations (Scopus)

Abstract

The effect of elevated external [K+] compared to luteinizing hormone-releasing hormone (LHRH) on gonadotropin secretion was studied in vitro in superfused pituitary fragments from cyclic female rats. Challenging proestrous but not estrous pituitaries with a 2-h pulse of 0.8 nM LHRH produces two distinct peaks in the curve for the first derivative of gonadotropin secretion versus time; the second peak exceeds the initial one and represents expression of LHRH self-priming. Challenging proestrous pituitaries with a 2-h pulse of raised [K+] results in an initial increase in secretion followed by a positive slope of the secretion rate curve for LH but a constant rate for follicle-stimulating hormone (FSH); the positive slope is blocked by cycloheximide and not found with estrous pituitaries pulsed with raised [K+]. Proestrous pituitaries exhibit a graded response to 10-min pulses of raised external [K+] from 10-91 mM for LH and 10-47 mM for FSH secretion. LHRH followed by elevated [K+] primed the LH and FSH response to the secretagogue, but the reverse sequence did not. The results show 1) a concentration dependence of elevated [K+]-induced LH and FSH secretion, 2) a LHRH specific initiation of priming that does not require the immediate presence of LHRH for its subsequent expression, and 3) a gonadotropin secretory response to elevated [K+] that varies during the estrous cycle and can be modified by protein synthesis inhibition or progesterone administration.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume7
Issue number2
StatePublished - 1983

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Gonadotropins
Gonadotropin-Releasing Hormone
Follicle Stimulating Hormone
Estrous Cycle
Cycloheximide
Progesterone
In Vitro Techniques
Rats
Derivatives
Proteins

ASJC Scopus subject areas

  • Biochemistry
  • Endocrinology
  • Physiology

Cite this

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abstract = "The effect of elevated external [K+] compared to luteinizing hormone-releasing hormone (LHRH) on gonadotropin secretion was studied in vitro in superfused pituitary fragments from cyclic female rats. Challenging proestrous but not estrous pituitaries with a 2-h pulse of 0.8 nM LHRH produces two distinct peaks in the curve for the first derivative of gonadotropin secretion versus time; the second peak exceeds the initial one and represents expression of LHRH self-priming. Challenging proestrous pituitaries with a 2-h pulse of raised [K+] results in an initial increase in secretion followed by a positive slope of the secretion rate curve for LH but a constant rate for follicle-stimulating hormone (FSH); the positive slope is blocked by cycloheximide and not found with estrous pituitaries pulsed with raised [K+]. Proestrous pituitaries exhibit a graded response to 10-min pulses of raised external [K+] from 10-91 mM for LH and 10-47 mM for FSH secretion. LHRH followed by elevated [K+] primed the LH and FSH response to the secretagogue, but the reverse sequence did not. The results show 1) a concentration dependence of elevated [K+]-induced LH and FSH secretion, 2) a LHRH specific initiation of priming that does not require the immediate presence of LHRH for its subsequent expression, and 3) a gonadotropin secretory response to elevated [K+] that varies during the estrous cycle and can be modified by protein synthesis inhibition or progesterone administration.",
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AB - The effect of elevated external [K+] compared to luteinizing hormone-releasing hormone (LHRH) on gonadotropin secretion was studied in vitro in superfused pituitary fragments from cyclic female rats. Challenging proestrous but not estrous pituitaries with a 2-h pulse of 0.8 nM LHRH produces two distinct peaks in the curve for the first derivative of gonadotropin secretion versus time; the second peak exceeds the initial one and represents expression of LHRH self-priming. Challenging proestrous pituitaries with a 2-h pulse of raised [K+] results in an initial increase in secretion followed by a positive slope of the secretion rate curve for LH but a constant rate for follicle-stimulating hormone (FSH); the positive slope is blocked by cycloheximide and not found with estrous pituitaries pulsed with raised [K+]. Proestrous pituitaries exhibit a graded response to 10-min pulses of raised external [K+] from 10-91 mM for LH and 10-47 mM for FSH secretion. LHRH followed by elevated [K+] primed the LH and FSH response to the secretagogue, but the reverse sequence did not. The results show 1) a concentration dependence of elevated [K+]-induced LH and FSH secretion, 2) a LHRH specific initiation of priming that does not require the immediate presence of LHRH for its subsequent expression, and 3) a gonadotropin secretory response to elevated [K+] that varies during the estrous cycle and can be modified by protein synthesis inhibition or progesterone administration.

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