HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Desrues, L. Articles by Vaudry, H. Search for Related Content PubMed PubMed Citation Articles by Desrues, L. Articles by Vaudry, H.

Previous studies have demonstrated that TRH is a potent stimulator of -MSH secretion from frog pituitary melanotrophs. In order to determine the intracellular events responsible for TRH-evoked -MSH release, we have investigated the effect of TRH on polyphosphoinositide breakdown in frog pars intermedia. Neurointermediate lobes were labelled to isotopic equilibrium with myo-[³H]inositol.

TRH stimulated the rate of incorporation of [³H]inositol into the phospholipid fraction. The effect of TRH was concentration-dependent; half-maximal stimulation of -MSH release and inositol incorporation occurred at 12 and 28 nmol TRH/1 respectively. In prelabelled neurointermediate lobes, lithium (10 mmol/l) enhanced the radioactivity in inositol monophosphate, bisphosphate (IP₂) and trisphosphate (IP₃). LiCl (10 mmol/l) induced a 38% inhibition of -MSH release from perifused neurointermediate lobes but did not impair TRH-induced -MSH secretion. In the presence of LiCl, TRH (1 µmol/l) induced a transient increase of the radioactivity in IP₃, which was evident by 30 s and maximal by 1 min (+ 100%). TRH treatment also increased the radioactivity in IP₂, which reached a plateau after 5 min (+ 100%). The increase in radioactivity in IP₃ induced by TRH was closely paralleled by a rapid loss of [³H]phosphatidylinositol bisphosphate (PIP₂), which was maximal by 1 min (–70%).

These results indicate that, in frog pars intermedia, TRH-evoked -MSH secretion is coupled to breakdown of PIP₂. The data suggest that, in amphibian melanotrophs, as previously shown in GH₃ tumour cells and in rat pituitary mammotrophs, TRH causes rapid stimulation of polyphosphoinositide-hydrolysing phospholipase C.

This article has been cited by other articles:

				A. Belmeguenai, L. Desrues, J. Leprince, H. Vaudry, M.-C. Tonon, and E. Louiset Neurotensin Stimulates Both Calcium Mobilization from Inositol Trisphosphate-Sensitive Intracellular Stores and Calcium Influx through Membrane Channels in Frog Pituitary Melanotrophs Endocrinology, December 1, 2003; 144(12): 5556 - 5567. [Abstract] [Full Text] [PDF]

				R. Vazquez-Martinez, J. R. Peinado, J. L. Gonzalez de Aguilar, L. Desrues, M. C. Tonon, H. Vaudry, F. Gracia-Navarro, and M. M. Malagon Melanotrope Cell Plasticity: A Key Mechanism for the Physiological Adaptation to Background Color Changes Endocrinology, July 1, 2001; 142(7): 3060 - 3067. [Abstract] [Full Text] [PDF]

				L. Galas, M. Lamacz, M. Garnier, E. W. Roubos, M.-C. Tonon, and H. Vaudry Involvement of Protein Kinase C and Protein Tyrosine Kinase in Thyrotropin-Releasing Hormone-Induced Stimulation of {alpha}-Melanocyte-Stimulating Hormone Secretion in Frog Melanotrope Cells Endocrinology, July 1, 1999; 140(7): 3264 - 3272. [Abstract] [Full Text]

				M. Garnier, M. Lamacz, L. Galas, S. Lenglet, M.-C. Tonon, and H. Vaudry Pharmacological and Functional Characterization of Muscarinic Receptors in the Frog Pars Intermedia Endocrinology, August 1, 1998; 139(8): 3525 - 3533. [Abstract] [Full Text] [PDF]

				J. L. Gonzalez de Aguilar, M. M. Malagon, R. M. Vazquez-Martinez, I. Lihrmann, M.-C. Tonon, H. Vaudry, and F. Gracia-Navarro Two Frog Melanotrope Cell Subpopulations Exhibiting Distinct Biochemical and Physiological Patterns in Basal Conditions and under Thyrotropin-Releasing Hormone Stimulation Endocrinology, March 1, 1997; 138(3): 970 - 977. [Abstract] [Full Text] [PDF]