Somatostatin prevents the desensitizing action of growth hormone-releasing factor on growth hormone release |
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| Authors: | J Simard G Lefèvre F Labrie |
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| Affiliation: | 1. Department of Plant Biology and Plant Biotechnology, Ramakrishna Mission Vivekananda College, Mylapore, Chennai, Tamil Nadu 600 004, India;2. Department of Chemistry, Siddha Central Research Institute, Central Council for Research in Siddha, Arumbakkam, Chennai 600 106, Tamil Nadu, India;3. Pondicherry Centre for Biological Science and Educational Trust, Jawahar Nagar, Pondicherry 605 005, India;4. Biological Sciences Department, College of Science, King Faisal University, Hofuf 31982 Al Hassa, Saudi Arabia;1. Microbiology and Paediatric Dentistry Unit, Department of Medical, Oral and Biotechnological Sciences, University of Chieti, Via dei Vestini 31, 66013, Italy;2. Dental Materials and Medical Chemistry Unit, Department of Medical, Oral and Biotechnological Sciences, University of Chieti, Via dei Vestini 31, 66013, Italy;3. Paediatric Dentistry Unit, Department of Medical, Oral and Biotechnological Sciences, University of Chieti, Via dei Vestini 31, 66013, Italy;1. Department of Molecular and Cellular Sciences, Faculty of Advanced Sciences & Technology, Pharmaceutical Sciences Branch, Islamic Azad University (IAUPS), Tehran, Iran;2. Department of Microbiology, Faculty of Advanced Sciences and Technology, Pharmaceutical Sciences Branch, Islamic Azad University (IAUPS), Tehran, Iran;3. Department of Immunology, Pasteur Institute of Iran, Tehran, Iran;4. Recombinant Vaccine Research Center, Tehran University of Medical Sciences, Tehran, Iran;1. Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, Maharashtra, India;2. Institute of Bioinformatics, International Tech Park, Whitefield, Bangalore 560066, India;3. Manipal University, Madhav Nagar, Manipal 576104, India;4. Proteomics Lab, National Centre for Cell Science, Ganeshkhind, Pune, Maharashtra, India;1. Institute of Antibiotics, Huashan Hospital, Fudan University, Key Laboratory of Clinical Pharmacology of Antibiotics, National Health Commission, Shanghai, China;2. National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China;3. Department of Infectious Diseases, Huashan Hospital, Fudan University, Shanghai 200040, China;4. Shanghai Huashen Institute of Microbes and Infections, Shanghai 200052, China |
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| Abstract: | We have investigated the effect of prior exposure to somatostatin (SRIF) alone or in combination with growth hormone-releasing factor (GRF) on the subsequent cyclic AMP and GH responses to GRF in rat anterior pituitary cells in primary culture. The maximal 4.5-fold stimulation of GH release induced by a 3-hr incubation with GRF is reduced by 60% following a prior 3-hr exposure to 30 nM GRF. A 3-hr preincubation with GRF in the presence of 30 nM SRIF doubles spontaneous GH release while the maximal amount of GH released during a subsequent 3-hr exposure to GRF is similar to that measured in cells pretreated with control medium, thus completely preventing the loss of GH responsiveness induced by prior exposure to GRF. The prevention by SRIF of the desensitizing action of GRF on GH release is not observed on the cyclic AMP response which remains almost completely inhibited in GRF-pretreated cells. Similar protective effects are obtained when SRIF is incubated with prostaglandin E2 (PGE2), thus completely preventing the desensitizing action of PGE2 on GH release. Prior treatment with pertussis toxin completely prevents the protective action of SRIF on GH responsiveness. Pretreatment with GRF + SRIF increases by 85 and 60% the maximal amount of GH release induced by cholera toxin and 8-bromoadenosine 3',5'-monophosphate, respectively. The post-SRIF rebound effect on GH release occurs mainly during the first 30 min following withdrawal of the tetradecapeptide. The present data demonstrate that simultaneous preincubation with SRIF and GRF prevents the marked inhibition of GH release during subsequent exposure to GRF.(ABSTRACT TRUNCATED AT 250 WORDS) |
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