PubMed · 4886193
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
G Peters. 1968-11-22. [Estriol].. https://pubmed.ncbi.nlm.nih.gov/4886193/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
The neuropeptides angiotensin II (AngII) and oxytocin (OT) play important but opposing roles in the regulation of sodium appetite in the rat, AngII as a stimulatory peptide and OT as an inhibitory peptide. Adrenal steroids increase the density of AngII receptors in brain following in vivo administration, although the neuroanatomical and subtype specificity have not been thoroughly examined. Furthermore, previous studies demonstrate that adrenalectomy (ADX) leads to a reduction in OT receptors, although regions associated with sodium appetite remain to be examined. In the present study, quantitative receptor autoradiography was used to locate regions where perturbations in circulating adrenal steroids affect the density of oxytocin receptors and the angiotensin receptor subtypes AT1 and AT2. The results show that ADX results in a small, but significant decrease in AT1 expression in the paraventricular nucleus of the hypothalamus, subfornical organ, and the area postrema. That this effect is reversed by either aldosterone or low-dose corticosterone replacement suggests that occupancy of the mineralocorticoid receptor is responsible for the steroid effect. No changes were observed in AT2 or OT receptors in nuclei associated with sodium appetite, indicating that perturbations in adrenal steroids did not affect these receptors in brain regions implicated in the control of salt appetite.
N-terminal sequences involved in transcription activation by the human mineralocorticoid receptor (hMR) have yet to be defined. We have addressed this issue and generated overlapping internal deletion mutants hMRDelta59-162, hMRDelta59-247, hMRDelta59-328, hMRDelta162-247, hMRDelta247-328, hMRDelta247-382, and hMRDelta328-382 with intact DNA-binding and hormone-binding domains. A second set of mutant receptors with unique BglII sites was generated to facilitate the isolations of fragments. Immunodetection with anti-hMR peptide antibodies and hormone-binding assays showed that the mutations did not affect the expression of the receptors or ability to bind aldosterone. Distribution of aldosterone binding activity of wild type and deletion mutants expressed in HeLa cells was predominantly nuclear. Furthermore, deletion of sequences between 59 and 390 did not affect DNA binding activity. Transfection studies with HeLa cells revealed a region around residue 247 that was crucial for normal receptor function. Deletion of amino acids 59-162 did not affect the transcriptional activity of the hMR. However, deletion of sequences 247-382 and 328-382 markedly decreased the transcription activation function. The induction of the reporter gene by the chimera hGRDelta71-262/hMR328-382 was 2-fold higher than with the wild type hGR, but 200-fold when compared with hGRDelta71-262, indicating that the AF-1 domain is located between positions 328 and 382 in the hMR.
To assess the role of each of the four cysteine residues in the hormone binding domain (HBD) of the human mineralocorticoid receptor (hMR), we have separately substituted C808, C849, C910, and C942 into serine. These mutations were created in the G595-K984 hMR receptor fragment which encompasses the DNA binding domain, the hinge region, and the hormone binding domain. Each mutant was further analyzed by steroid binding assays and transactivation assays using wild-type and mutant proteins expressed in vitro in the reticulocyte lysate. While the C910S mutant exhibited similar wild-type G595-K984 receptor binding properties for aldosterone, the C808S mutant affinity was 3.5-fold higher. In contrast, the C849S mutant showed a drastic drop in affinity for aldosterone and the mutant C942S was unable to bind the steroid. Affinities for the antagonist progesterone were also determined. C808S, C849S, and C910S were found to bind progesterone better than aldosterone (about a 2-fold increase in their affinities). Mutant C942S failed to bind any steroid tested (aldosterone, progesterone, cortisol, and the synthetic antagonist RU26752). No change in the specificity toward various agonists and antagonists could be observed with the mutants when compared to the wild-type G595-K984. When transactivation assays were performed, the properties of mutants C808S and C910S were similar to those of the wild-type G595-K984, while mutant C849S showed reduced sensitivity and C942S was devoid of any transcriptional activity. Our data indicate that C849 and C942 are critical for the ligand binding process of hMR. Moreover, C942 might be involved in a direct contact with the 20-keto group of the steroid.