Differential estrogen receptor binding of estrogenic substances: a species comparison.

The study investigated the ability of 34 natural and synthetic chemicals to compete with [3H]17beta-estradiol (E2) for binding to bacterially expressed glutathione-S-transferase (GST)-estrogen receptors (ER) fusion proteins from five different species. Fusion proteins consisted of the ER D, E and F domains of human alpha (GST-hERalphadef), mouse alpha (GST-mERalphadef), chicken (GST-cERdef), green anole (GST-aERdef) and rainbow trout ERs (GST-rtERdef). All five fusion proteins displayed high affinity for E2 with dissociation constants (K(d)) ranging from 0.3 to 0.9 nM. Although, the fusion proteins exhibited similar binding preferences and binding affinities for many of the chemicals, several differences were observed. For example, alpha-zearalenol bound with greater affinity to GST-rtERdef than E2, which was in contrast to other GST-ERdef fusion proteins examined. Coumestrol, genistein and naringenin bound with higher affinity to the GST-aERdef, than to the other GST-ERdef fusion proteins. Many of the industrial chemicals examined preferentially bound to GST-rtERdef. Bisphenol A, 4-t-octylphenol and o,p' DDT bound with approximately a ten-fold greater affinity to GST-rtERdef than to other GST-ERdefs. Methoxychlor, p,p'-DDT, o,p'-DDE, p,p'-DDE, alpha-endosulfan and dieldrin weakly bound to the ERs from the human, mouse, chicken and green anole. In contrast, these compounds completely displaced [3H]E2 from GST-rtERdef. These results demonstrate that ERs from different species exhibit differential ligand preferences and relative binding affinities for estrogenic compounds and that these differences may be due to the variability in the amino acid sequence within their respective ER ligand binding domains.

Translocation of aged cyclodiene insecticide residues from soil into forage crops and pastures at various growth stages under field conditions.

Field trials were conducted to measure translocation of pesticides by summer and winter forage/pasture species from soil containing aged residues of heptachlor and, to a lesser extent, dieldrin. Substantial amounts of heptachlor epoxide, and lesser amounts of gamma-chlordane were translocated to plants from contaminated soil. Residue levels varied with crop species and stage of plant development. In summer crops residues were higher in soybean > cowpeas > lab-lab > Sorghum > millet > sweet saccaline at the grazing and mature stages. Compared to glasshouse studies undertaken previously, residues in crops grown under field conditions were much lower. This apparently reflects the lower soil moisture levels and the reduced rates of translocation. Heptachlor residues in winter crops were highest in Saia oats > Berseem clover > Haifa clover > Cassia oats > Tetila ryegrass > Schooner barley > Shaftal clover > Hunter river lucerne at the grazing stage. There were no detectable levels in barley and oats at the mature stage. No dieldrin residues were translocated into the various crop species.

Dieldrin, Ca and P balance, and characteristics of the egg in the quail (Coturnix coturnix japonica).

A study was made of the Ca and P balance, Ca and P content in the femur, physical characteristics of the egg, mineral structure of the shell, and the number of eggs in quails treated with dieldrin (20 mg/kg of diet) for 48 days. The diet contained 3.24% Ca and 0.72% P. The Ca and P balance, the bone contents of Ca and P and the calcemia in the males were not changed by the pesticide. In the females, the pesticide decreased the amount of excreted Ca and Ca in the egg, for which reason the coefficient of nutritive utilization (CNU), the coefficient of corporal retention (CCR), and the Ca level in the femur were greater in treated laying quails. The calcemia remained stable, and the balance of P was not significantly modified by the dieldrin. The study of weight, size, and strength of the egg did not reveal any influence of the dieldrin, and egg production fluctuated throughout the test period.

Dieldrin and DDT in the tissues of mice fed aldrin and DDT for seven generations.

Seven-Generation Study (P-F6): The concentration and total retention of dieldrin or p,p'-DDT and metabolites were determined in the total carcass of Swiss-Webster mice fed dietary supplements of aldrin 5 or 10 ppm, or DDT 100 ppm, to age 260 days. All groups showed a significant increase in total body retention (and concentration) of dieldrin or total DDT in the total carcass of the F1, F2, and F3 generations. Generally, these increases were related directly to increases in total body lipids, when compared with the P generations. The control (pesticide-free) diet was fed to all F4 generation experimental mice from weaning to age 260. The pesticides absorbed by these animals while in utero and via lactation were found, at the time of sacrifice, to have been excreted completely. When the experimental diets were resumed with the weanlings of the F2 generations, a repetition of the general findings in the P and F1 generations was noted-demonstrating that pesticide retention and total body lipids are closely interrelated, and that a high body lipid content favors a high retention rate of these fat-soluble pesticides. These results support our earlier studies in rats (Deichmann et al., 1972) and investigations with cirrhotic human livers with severe fatty infiltration (Oloffs et al., 1974). Conception became more delayed with each succeeding generation, requiring some degree of "selective" breeding of the F4, F5, and F6 generations.