Hemolytic properties of hexachlorophene and related chlorinated bisphenols

Hexachlorophene retinopathy in suckling rats. A light- and electron-microscopic study of short-term and long-term effect of hexachlorophene intoxication on the retina of young rats

Hexachlorophene (HCP) in very large doses has a toxic effect on the retina of adult rats. The present study examined the sensitivity of the developing retina to smaller doses and its ability to recover from neurotoxic damage. Suckling rats were intoxicated with HCP added to the mothers' diet. The retinae of the pups were examined by light and electron microscopy for early and late effects. All dose levels above 100 ppm caused vacuolar degeneration of the outer segments of photoreceptor cells within 14 days of intoxication, followed by degeneration of the inner segments after 28 days. The cell bodies of photoreceptor cells and all other retinal layers remained normal. Suckling intoxicated with HCP (100 - 500 ppm) added to the mothers' diet for 28 days and then withdrawn, showed no recovery of the outer or inner segments o photoreceptors when examined up to 150 days later. In addition, extensive degeneration and loss of photoreceptor cell occurred after withdrawal of HCP and the degenerative process extended to involve the inner nuclear layer. The rate of appearance of pathological changes was proportional to the total amount of ingested HCP. This study showed that photoreceptor cells in newborn rats are highly sensitive to HCP. The retinal lesions were irreversibly an continued to progress by continued trans-synaptic degeneration after withdrawal of the toxic agents.

Effects of chlorinated bisphenols on torula yeast glucose-6-phosphate dehydrogenase

Chlorinated bisphenol antibacterial and antifungal agents are potent inhibitors of torula yeast glucose-6-phosphate dehydrogenase (G6PD). Several compounds were tested, including hexachlorophene [HCP; 2,2'-methylenebis(3,4,6-trichlorophenol)]; 2,2'-oxybis(tetrachlorophenol); 2',4-dihydroxy-2,3,3',5,5',6-hexachlorodiphenylmethane; 2,2'-methylenebis(3,4-dichlorophenol) (3,4-TCP); bithionol [2,2'-thiobis(4,6-dichlorophenol)]; 2,2'-methylenebis(3,5-dichlorophenol); 2,2'-dihydroxy-3,3',5,6,6'-pentachlorodiphenylmethane; 2,2'-methylenebis(4-chlorophenol) (DCP); 2,2'-methylenebis(4,6-dichlorophenol); and the related uncoupler 2,4-dinitrophenol. The relative inhibitory activity of the chlorinated bisphenols tended to increase with degree of chlorination of the aromatic rings. the concentrations of the bisphenols that caused 50% inhibition ranged from 2.5 micrometers for 2,2'-oxybis(tetrachlorophenol) to 40 micrometers for 2,2'-methylenebis(4,6-dichlorophenol) under comparable assay conditions. More detailed kinetic analysis showed that, as with HCP, the inhibition of G6PD by 3,4-TCP and DCP followed noncompetitive kinetics. Calculations from the kinetic data gave apparent inhibition constant (Ki) values for 3,4-TCP of 267 micrometers with G6P and 308 micrometers with NADP, and for DCP of 697 micrometers with both G6P and NADP.

Effects of halogenated antibacterials on the erythrocyte membrane

The influence of halogenated antibacterials on membrane structure and function was investigated using the human erythrocyte membrane as a model. Measurements of hemolysis in isotonic solution, altered membrane permeability, and stabilization against hypotonic hemolysis resulting from exposure of erythrocytes to halogenated antibacterials served as criteria of membrane-related effects. The hemolytic potency of the compounds studied differed widely, decreasing in the order hexachlorophene (HCP) greater than 2,2'-methylenebis(3,5-dichlorophenol) (3,5-TCP) greater than 2,2'-methylenebis(3,4-dichlorophenol) (3,4-TCP) approximately equal to 2,2'-methylenebis(4,6-dichlorophenol) (4,6-TCP) greater than 2,2'-methylenebis(4-chlorophenol) (DCP) greater than 3,4'-tribromosalicylanilide (TBS) approximately equal to 3,3',4',5-tetrachlorosalicylanilide (TCSA). Each of the antibacterials tested stabilized the erythrocyte against hypotonic hemolysis, although there were marked differences in the concentrations required to afford maximum stabilization as well as in the extent of protection. The observed order of protective effectiveness was HCP greater than 3,4-TCP greater than 4,6-TCP greater than DCP approximately equal to TCS greater than TBS. As shown by measurements of the first-order rate constant for K+ efflux, the permeability of the erythrocyte membrane to K+ was increased upon exposure to the antibacterials, with the effect of HCP greater than 3,4-TCP greater than 4,6-TCP approximately equal to 3,4-TCP greater than DCP approximately equal to TCS greater than TBS. These results indicate that halogenated antibacterials are capable of perturbing mammalian membranes, a feature which may account in part for their mammalian toxicity.

Biochemical and pathological studies of myelin in hexachlorophene intoxication

Adult female rats were fed a diet containing 500 ppm hexachlorophene (HCP). Morphological study of brains from these animals showed vacuolation of the myelin sheaths due to separation of myelin lamellae at the minor dense line. However, myelin could be isolated from the brains of these animals in normal yield. The myelin isolated from HCP-fed animals had normal lipid and protein compositions as shown by analyses of the individual lipids and by disc gel electrophoresis of the proteins. Assay of the myelin-specific enzyme, 2',3'-cyclic nucleotide-3'-phosphohydrolase, showed normal specific activity in myelin obtained from HCP-fed rats. Brains of HCP-fed rats showed an increase in wet weight and a decrease in dry weight, with the chloroform-methanol insoluble fraction showing the greatest weight loss. During isolation of myelin from HCP-fed rats material was found floating over 0.32 M sucrose. This "floating fraction" contained a higher ratio of lipid to protein but the same relative proportions of the individual lipids as are found in myelin. The yield of "floating fraction" from each HCP-fed rat was less than 10 percent of the yield of myelin. Disc gel electrophoresis demonstrated the presence of the usual myelin proteins in this fraction, but with a slight increase in the relative amount of the low molecular weight basic protein. The data were compared to reports on the biochemistry of triethyltin poisoning, and it was concluded that vacuolation of myelin in HCP poisoning is probably due to increased permeability of myelin lamellae to water and electrolytes.