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Biomedical subjects

L Swennen

Publications and source records attributed to L Swennen.

12 recordsLinked to original sources
PubMed1985

Beta-adrenergic stimulation of adenosine-3',5'-monophosphate (c-AMP) accumulation and of prolactin and growth hormone secretion in rat anterior pituitary cell cultures.

The beta-adrenergic agonist 1-isoproterenol (ISO) (10(-9)-10(-7) M) provoked a prompt and profound increase of intracellular c-AMP accumulation in monolayer cultures of rat anterior pituitary. In superfused reaggregate cell cultures ISO also stimulated c-AMP outflow. The effect was blocked by propranolol and the highly selective beta 2-receptor blocker ICI 118.551. Epinephrine (E), norepinephrine (NE) and the highly selective beta 2-agonist zinterol (ZIN) also stimulated c-AMP accumulation. The order of potency ZIN greater than or equal to ISO greater than E much greater than NE together with the high potency of ICI 118.551 suggests the beta-effect is mainly through the beta 2-receptor subtype. The same concentrations of ISO strongly stimulated growth hormone (GH) release and, as previously shown, prolactin (PRL) release from superfused reaggregate cell cultures, but not luteinizing hormone or thyroid stimulating hormone release. Stimulation of PRL and GH release from these cultures was also induced by the adenylyl cyclase activator forskolin. Since interference of beta-adrenergic effects on contaminating fibroblasts or endothelial cells could be reasonably excluded, the present data suggest that beta-adrenergic stimulation of c-AMP accumulation in anterior pituitary cells elicits GH and PRL release.

Animals↗
PubMed1985

Beta-adrenergic stimulation of adenosine-3',5'-monophosphate (c-AMP) in primary cultures of rat anterior pituitary cell populations separated by unit gravity sedimentation. Relationship to growth hormone and prolactin release and to nonsecreting cells.

The effect of the beta-adrenergic agonist isoproterenol (ISO) on c-AMP accumulation and on growth hormone (GH) and prolactin (PRL) release was studied in primary cultures of anterior pituitary cell populations with different proportional number of somatotrophs and lactotrophs, obtained by velocity sedimentation at unit gravity. ISO stimulated c-AMP levels in highly-enriched lactotroph (approximately 70%) as well as in highly-enriched somatotroph (approximately 65%) populations. ISO-stimulated c-AMP accumulation was attenuated by dopamine (DA) in highly enriched lactotroph but not somatotroph populations. In a small-cell population consisting of a much lower proportional number of lactotrophs and somatotrophs, the proportional increase of c-AMP accumulation was several times higher than in the other populations and the effect was not suppressible by DA. In this small-cell population, GH but not PRL release was more responsive to ISO than in the other populations. The present observations are consistent with the interpretation that the changes in c-AMP levels induced by ISO originate in part in somatotrophs and lactotrophs. However, the present data also demonstrate that the most responsive cell population in terms of c-AMP accumulation consists of small cells. The majority of these cells could not be identified. The possibility that these cells may be nonsecreting folliculostellate cells is discussed.

Animals↗
PubMed1981

Preferential stimulation by aurintricarboxylic acid of DNA-dependent RNA polymerase II activity in isolated larval nuclei of Artemia salina.

Aurintricarboxylic acid was found to stimulate preferentially RNA polymerase II activity in isolated nuclei of Artemia salina larvae. Studies on the in vitro transcription of a homologous chromatin indicate that this dye induces changes in the chromatin so as to enhance its template capacity for free RNA polymerase. Both free RNA polymerases I and II are equally sensitive to this dye in the absence of chromatin template. RNA polymerase II, however, becomes highly resistant to aurintricarboxylic acid when it is actively transcribing the chromatin template, whereas RNA polymerase I remains extremely sensitive even in the transcription complex. Therefore, in isolated nuclei, a preferential stimulation of alpha-amanitin-sensitive, but not-resistant RNA synthesis by aurintricarboxylic acid can be observed.

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