In search of an experimental model that would simulate the association between proteinuria and salt sensitivity in humans, we studied protein excretion in the Sabra rat model of salt susceptibility. Monthly measurements of urinary protein excretion in animals fed standard rat chow revealed that normotensive salt-sensitive SBH/y developed proteinuria that averaged 65 +/- 7 mg/day (n = 10) at 9 mo, whereas proteinuria in normotensive salt-resistant SBN/y was 39 +/- 4 mg/day (n = 10) (P < 0.01). Histopathological evaluation revealed focal and segmental glomerulosclerosis (FSGS) lesions grade 2 in SBH/y and normal histology in SBN/y. To amplify the differences between the strains, uninephrectomy was performed. At 9 mo, proteinuria in SBH/y with one kidney (SBH/y-1K) was 195 +/- 12 mg/day (n = 10) and in SBN/y was 128 +/- 10 mg/day (n = 10) (P < 0.001); histopathology revealed FSGS grade 3 in SBH/y-1K and grade 1-2 in SBN/y-1K. To determine the effect of salt loading, animals were provided with 8% NaCl in chow, causing hypertension in SBH/y but not in SBN/y. Proteinuria markedly increased in both SBH/y with two kidneys (SBH/y-2K) and SBH/y-1K, but not in SBN/y; histopathology revealed FSGS grade 1-2 in SBH/y-2K, grade 2 in SBH/y-1K, no lesions in SBN/y-2K, and grade 0-1 in SBN/y-1K. We concluded that the SBH/y strain is more susceptible to develop proteinuria and glomerulosclerosis than SBN/y. In search for the genetic basis of this phenomenon, we investigated the role of candidate proteinuric gene loci. Consomic strains were constructed by introgressing chromosome 1 (which harbors the rf-1 and rf-2 proteinuric loci) or chromosome 17 (which harbors rf-5) from SBH/y onto the SBN/y genomic background. The resulting consomic strains developed marked proteinuria that was severalfold higher than in SBN/y-1K; histopathological evaluation, however, revealed FSGS lesions grade 1-2, similar to those found in SBN/y-1K and less severe than in SBH/y-1K. These results suggest a functional role of gene systems located on chromosomes 1 and 17 in inducing proteinuria in the salt-susceptible Sabra rat strain. These genetic loci do not appear to harbor major genes for glomerulosclerosis.

Superfused interrenal tissue of Sarotherodon aureus responded to ACTH with increased release of cortisol. The response to ACTH of interrenal tissue taken from fish treated with the organochlorine insecticide 1,1-dichloro-2-(o-chlorophenyl)-2-(p-chlorophenyl) ethane (o,p-DDD; 50 mg/kg) in vivo was almost totally abolished. Lower doses were less effective. The response was also suppressed by exposure in vitro of the interrenal tissue to the organochlorine; there seemed to be a dose-response to o,p-DDD over the range of 0.023 to 1 mg/l. Also 1,1-dichloro-2,2-bis (p-chlorophenyl) ethylene (p,p'-DDE) was effective in suppressing the response to ACTH at concentrations of 50--150 mg/l; 1,1,1-trichloro-2,2-bis (p-chlorophenyl) ethane (p,p'-DDT) or the polychlorinated biphenyl, Aroclor 1254, were ineffective at 50 mg/l. No suppressive effect of o,p-DDD on output of cortisol could be detected in superfusion when N6,O2'-dibutyryl cyclic AMP (20 mmol/L) was substituted for ACTH. This may indicate that the interference of o,p-DDD with the interrenal response to ACTH results from an interruption in the generation of cyclic AMP.

The purpose of this study was to investigate possible effects of organochlorine residues on cortisol balance in a freshwater fish. The combined stress of netting, handling and blood sampling in Sarotherodon aureus normally results in a twofold increase of circulating cortisol, within 30-60 min. Fish treated with o,p'DDD (50 mg kg-1) had higher resting level of cortisol than before treatment (1 55.8 k 12.7 v. 86.9 f 11.2 ng m1-I; n = 16). No further increase in cortisol level occurred in these fish after exposure to stress; this inability to respond was maintained for more than 120 days. A recovery of the response to ACTH by superfused interrenal tissue from the treated fish was observed 255 days after treatment. Successive blood sampling of o,p'DDD-treated fish, injected intracardially with labelled cortisol, have shown that the half-life of the steroid in the circulation is prolonged by 370% compared with controls. The hepatic metabolism of cortisol was studied by incubating liver slices with the labelled hormone. Hepatic tissue from o,p'DDD-treated fish metabolized cortisol slower than livers from controls. The high resting level of cortisol in plasma of fish treated with o,p'DDD may be attributed to the retarded metabolism of the steroid by the liver. The lack of augmented cortisol levels in response to stress is attributed to the interference of the organochlorine with the response of the interrenal tissue to the stress-induced surge of endogenous ACTH.

An electron microscopic description is presented of the mitochondria-rich ' chloride ' cells of the gill epithelium in the cichlid fish TiZapiu uurea kept in freshwater or adapted to seawater and injected with the pesticide p,p'DDT. The ' chloride ' cells may have a light or dark (electron dense) appearance. Dark ' chloride ' cells are more common in seawateradapted than in freshwater T. auren. Characteristic features of ' chloride ' cells include an abundance of mitochondria and anelaborate tubular reticulum, which communicates directly with the basal and lateral membranes of the cells. The apical portion of the ' chloride ' cells is often larger in seawater-adapted than in freshwater fish. Differences in ' chloride ' cell ultrastructure, which can possibly be associated with a response to different salinities, are described and discussed. No significant ultrastructural differences are detectable in response to injections of the pesticide.

The effect of ACTH on cortisol concentration in the plasma of the carp has been studied; cortisol was determined using a competitive protein-binding radioassay. Blood was sampled at 12.00 h (the diurnal minimum) by cardiac puncture. The plasma cortisol level of undisturbed carp (blood obtained 1--3 min after netting) was 16 +/- 14 (S.E.M.) ng/ml. One hour after injection of ACTH (1-0 i.u./100 g body wt., i.m.) the level of cortisol increased to 415 +/- 62 ng/ml and reached a maximum of 656 +/- 62 ng/ml after 2 h. The level of cortisol in saline-injected control carp after 2 h was 72 +/- 33 ng/ml. A transient rise of cortisol was noted in both groups 30 min after injection (315 +/- 51, 315 +/- 62 ng/ml). This was attributed to a surge of endogenous ACTH, presumably due to handling. Carp head kidneys were superfused in vitro. They released cortisol spontaneously, but the releasing rate declined exponentially and reached a minimum after 135 min. Addition of ACTH to the medium was followed by a prompt increase in cortisol release. The rate of cortisol release was maximal 30--45 min after addition of ACTH and was identical to the rate at the beginning of the superfusion.