The presence of cortisol receptors in the human amnion.

Cytosol extracts of human amnion tissue contained high affinity binding of cortisol (Ka=2.48+/-1.06 x 10(9) M(-1); n = 30) and low capacity binding of cortisol (Nmax=279+/-15.5 fmol mg(-1) protein). Kinetic studies of cortisol binding resulted in a similar value of Ka to that obtained by Scatchard analysis. Nuclear extracts of amnion tissue contained high affinity binding of cortisol (Ka=5.8+/-1.91 x 10(7) M[-1]) and low binding capacity (Nmax=91.4+/-21.4 fmol mg(-1) protein). Ka values were an order of magnitude higher in cytosol than in blood serum when amnion and blood were obtained from the same individuals. Differences in competitive ligand binding, especially dexamethasone, were observed between the amnion receptor and transcortin in serum. Gel permeation chromatography gave only one peak at 320 kDa for amnion receptor and only one peak at 48 kDa for transcortin from serum. When amnion tissue was incubated with or without cortisol, cytosol receptor activity was significantly lower in cortisol treated tissue than in control. The nuclear extracted receptor activity was significantly higher in cortisol treated tissue than control. The Ka values from cortisol treated tissue were significantly lower from control. Together the data support the presence of a specific cortisol receptor in the human amnion that is different from transcortin.

Seasonal changes in osmoregulation, cortisol, and cortisol receptor activity in the gills of parr/smolt of steelhead trout and steelhead-rainbow trout hybrids, Oncorhynchus mykiss.

Steelhead and hybrid trout (rainbow trout male, steelhead female) presmolts and smolts, Oncorhynchus mykiss, exposed to 30/1000 seawater (SW) for 24 hr manifested progressively lower plasma sodium values from December to May. The increase in plasma sodium after 24 hr in SW diminished significantly after March, with the hybrids (which were heavier in weight than the steelheads) reaching their peak osmoregulatory ability in the middle of April, and the steelheads in late May. In fresh water there was little difference in plasma osmotic concentration but steelhead plasma chloride fell significantly from March 30 levels to May 23 levels, whereas hybrid plasma chloride levels did not change during this time. In steelheads but not hybrids, plasma cortisol correlated negatively with plasma sodium of fish exposed 24 hr in SW. However, in both steelheads and hybrids, plasma sodium values 24 hr after SW exposure had an inverse correlation with cytosol cortisol from the gills. Again, in both steelheads and hybrids, plasma values of fish exposed 24 hr in SW correlated positively with cytosol receptor activity. In hybrids, the nuclear extract receptor activity, Nmax, increased significantly until late March and then dropped significantly thereafter. In steelheads, there were no significant differences but Nmax followed the same trends as occurred in hybrids. Thus seasonal changes in cortisol and cortisol receptors in steelhead occur during smoltification and preparation for marine life and suggest an important role for cortisol. In hybrids there appears to be a reduction in seasonality.