Effect of pre-incubation with different concentrations of LH-RH on subsequent LH release caused by supramaximally active amounts of LH-RH; Role of LH-RH-induced protein synthesis

Koning, J. de; Dieten, J. A. M. J. van; Rees, G. P. van

doi:10.1016/0024-3205(77)90240-5

Cited by 17 publications

(11 citation statements)

References 6 publications

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“…The initial increase in sensitivity ap¬ peared, like that seen in other in vitro prepara¬ tions (de Koning et al 1977), to be dependent on de novo protein synthesis for it was abolished by protein synthesis inhibitors. It was also associated with the ovarian hormonal status of the animals from which the tissue had been derived.…”

Section: Discussionmentioning

confidence: 84%

“…The increased responsiveness of the gonadotrophs to the releasing hormone, fre¬ quently called the priming effect, has been de¬ monstrated in vivo (Aiyer et al 1974) and in vitro using static incubations of pituitary fragments (de Koning et al 1977) or perifused cultured cells (Smith & Vale 1981). However, relatively few workers (Evans et al 1984) in the field have been able to demonstrate the priming phenomenon in acutely dispersed perifused cells.…”

Section: Discussionmentioning

confidence: 97%

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Changes in the responsiveness of perifused rat adenohypophysial cells to repeated stimulation with luteinizing hormone releasing hormone

Buckingham

Cover

1986

Acta Endocrinologica

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The ability of luteinizing hormone releasing hormone (LRH) to stimulate the release of luteinizing hormone (LH) from columns of enzymatically dispersed perifused adenohypophysial cells is being used to study the mechanisms controlling the secretion of LH. LRH stimulated the release in vitro of LH from columns of rat pituitary cells. However, when exposed repeatedly (1 pulse every 12 min) to the same submaximal dose (8 nmol/l) of LRH the cells always exhibited a marked progressive increase and subsequent decrease in their responsiveness. Similar effects occurred when the interval between pulses was extended to 20, 30 or 45 min. The enhanced responsiveness of the cells was prevented by the inclusion of protein synthesis inhibitors, cycloheximide or puromycin, in the perifusion fluid. Cells removed from rats ovariectomized 14 days previously also failed to exhibit increased responsiveness when stimulated repeatedly with LRH. LH secretion was also elicited by K+ (50 nmol/l), 8-bromoadenosine 3\m=' \-5\m=' \-cycl i cmonophosphate (8-Br-cAMP, 6 nmol/l), 8-bromoguanosine 3\m=' \-5\m=' \-cyclicmonophosphate (8-Br\x=req-\ cGMP, 6 nmol/l) and a calcium ionophore (A23187, 40 \g=m\mol/l)but the responses to these secretagogues differed markedly from those to LRH for the tachyphylaxis which resulted from repeated exposure was not preceded by an increase in responsiveness. The decreased responsiveness to K+ developed in parallel with that to LRH. Diminished responses to the cyclic nucleotides and the Ca++ ionophore developed more rapidly, but the refractory cells responded readily to stimulation with LRH or K+. The results suggest that the increased responsiveness of the perifused pituitary cells induced by LRH is associated with steroid-dependent protein synthesis and that the secretion of LH elicited by its releasing hormone does not involve cAMP or cGMP.

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Section: Discussionmentioning

confidence: 84%

Section: Discussionmentioning

confidence: 97%

Changes in the responsiveness of perifused rat adenohypophysial cells to repeated stimulation with luteinizing hormone releasing hormone

Buckingham

Cover

1986

Acta Endocrinologica

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“…Moreover, since it may be assumed that injections of OB in rats also decreased endogenous release of LH-RH (see also [11]), the observed decay in the rate of LH release from glands from OB-pretreated rats might have been caused by a fast depletion of endogenous LH-RH-induced factors related to the synthesis of protein [1,7]. These problems can be overcome by pre-exposure of the pituitary glands to a high concentration of LH-RH only for 2 h, since then subsequently LH-RH-induced release of LH has become independent of further synthesis of protein for at least 4 h of incubation [ 1,6,7].…”

Section: Inhibitory Effect Of Obmentioning

confidence: 99%

“…Previous studies demonstrated that LH-RH-induced LH release from pituitary glands in vitro became independent of protein synthesis when the glands had been pre-exposed to either high endogenous or exogenous LH-RH levels [ 1,6,7]. The use of pituitary glands from ovariectomized (OVX) rats from which LH release normally is independent of protein synthesis, in any case after pretreatment with LH-RH, therefore provides a suitable experimental model to investigate to what extent actions of oestrogens themselves are dependent on protein synthesis.…”

Section: Introductionmentioning

confidence: 99%

Different effects of inhibitors of protein synthesis on the inhibited and augmented LH response of pituitary glands from ovariectomized rats to LH‐RH in vitro after pretreatment with oestradiol‐17β‐benzoate in vivo

Dieten¹,

Tijssen²,

Koning³

et al. 1982

FEBS Letters

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“…Previous investigations have clarified some aspects of the mechanisms underlying the alterations in the patterns of release of LH stimulated by LH-RH (de Koning, van Dieten & van Rees, 1976Rees, , 1977Rees, , 1978de Koning, van Dieten, Tijssen & van Rees, 1979). It was demonstrated that LH-RH initiates different intracellular events which mediate release of LH by means of separate pathways.…”

Section: Introductionmentioning

confidence: 97%

Effect of Ca2+ deprivation on release of luteinizing hormone induced by luteinizing hormone releasing hormone from female rat pituitary glands in vitro

Koning¹,

Tijssen²,

Dieten³

et al. 1982

Journal of Endocrinology

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Continuous exposure of hemi-pituitary glands from intact female rats to LH releasing hormone (LH-RH) in vitro displayed three phases in the pattern of LH release: during the first hour release of LH was low (first phase response), then it increased to a higher level during the second hour and remained constant during the next 2 h (second phase response), after which there was a refractoriness of LH release (third phase response). The initial phase response of pituitary glands from intact rats was blocked by EGTA (a Ca2+ chelator) but there was a small but significant increase in the rate of LH release during the second phase response. This increase could be prevented by inhibition of protein synthesis by cycloheximide. Cycloheximide and EGTA did not affect basal release of LH by glands from intact rats, neither did EGTA affect the high basal release of LH by glands from ovariectomized rats. However, the LH-RH-induced release of LH from pituitary glands of ovariectomized rats, which did not show the initial phase of low LH release, was completely suppressed by EGTA throughout a 4-h incubation period.The pattern of LH release stimulated by the combination of N6-monobutyryl cyclic AMP and theophylline (mbcAMP/theophylline) showed an initial phase of low LH release lasting 4 h after which it increased. The magnitude of the effect was small compared with the action of LH-RH. As it did with LH-RH, EGTA completely blocked the initial response, but allowed a small increase in the rate of LH release thereafter; this increase could also be blocked by inhibition of protein synthesis.Addition of EGTA to media during pretreatment of pituitary glands from intact rats with either LH-RH or mbcAMP/theophylline did not impair the facilitatory effect of these secretagogues on the responsiveness of the glands to subsequent exposure to LH-RH and cycloheximide and normal Ca2+ levels. The restoration of Ca2+ levels after withdrawal neither affected basal nor LH-RH-induced release of LH.Exclusion of Ca2+ from the media during a 6-h incubation of pituitary glands from intact rats with LH-RH prevented the glands from becoming refractory to subsequent stimulation by LH-RH, which occurs when normal Ca2+ concentrations are present.The results suggested that extracellular Ca2+ is obligatory for LH release and the induction of refractoriness by LH-RH. In contrast, that part of the action of LH-RH which is cyclic AMP-mediated and protein synthesis-dependent is not affected by withdrawal of extracellular Ca2+.

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Effect of pre-incubation with different concentrations of LH-RH on subsequent LH release caused by supramaximally active amounts of LH-RH; Role of LH-RH-induced protein synthesis

Cited by 17 publications

References 6 publications

Changes in the responsiveness of perifused rat adenohypophysial cells to repeated stimulation with luteinizing hormone releasing hormone

Changes in the responsiveness of perifused rat adenohypophysial cells to repeated stimulation with luteinizing hormone releasing hormone

Different effects of inhibitors of protein synthesis on the inhibited and augmented LH response of pituitary glands from ovariectomized rats to LH‐RH in vitro after pretreatment with oestradiol‐17β‐benzoate in vivo

Effect of Ca2+ deprivation on release of luteinizing hormone induced by luteinizing hormone releasing hormone from female rat pituitary glands in vitro

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