546 Articles of general interest-Fd Cosmet. Toxicol. Vol. 17, no. 5

in the blood and testes after 0.2%48 hr. Studies were The exact role played by these and possibly other also carried out on testes perfused via the testicular factors in the damaging effects exerted on the testis by artery. By these means it was possible to assess how Cd remains to be established. The problem continues much of the carbonic anhydrase activity in the testis to attract wide interest, however, and it may be that was contributed by the erythrocytes in the circulating the placing of a few more key pieces will enable the blood and how much was derived from the local tis- rest of the jigsaw to be fitted into place. sues. From the findings, it was concluded that alter- ations in the carbonic anhydrase activity of the testes following Cd administration reflected changes in the blood content and therefore in erythrocyte carbonic anhydrase in the organ. [P. Cooper-BIBRA]

CADMIUM AND THE PROSTATE

In addition to the affinity of cadmium (Cd) for the testis (see above), there is considerable evidence link- ing occupational exposure to Cd with diseases of the prostate, including prostatic carcinoma (Khare er al. Res. Commun. them. Path. Pharmac. 1978, 20, 351; Kipling & Waterhouse, Lancet 1967, I, 730; Potts, Ann. occup. Hyg. 1965, 8, 55). The lateral prostate of rhe rat contains high levels of zinc, the uptake of which is regulated by testosterone and affected by Cd (Timms et al. Virchows Arch. Abr. B Zellpath. 1977, 25, 33) and direct injection of Cd into the rat prostate has been shown to induce local carcinoma (Aughey YI al. Br. J. Ural. 197547, 185). Whether the action of Cd on the prostate is principally a direct effect or an indirect result of the lowering of testosterone levels has been in some doubt, however.

A study designed by Timms et al. (lot. cit.) to demonstrate whether direct ultrastructural changes could be demonstrated in the prostate of Cd-treated rats prior to the lowering of testosterone levels has indicated that Cd does exert some direct effect on this organ as well as on androgen levels. The ultra- structure of the lateral prostate of the rat after a single SC dose of 0.02 mmol CdCl,/kg body weight was examined at intervals of l-20 days. Zinc and Cd in tissues were estimated by atomic absorption spec- troscopy. The zinc content of the prostate declined after this administration of Cd, although that of the testes did not alter appreciably. The dry-weight con- tent of Cd was tenfold higher in the prostate than in the testis, and continued to increase for the first 10 days. Plasma testosterone fell to 20% of its initial value within 2 days of Cd injection, and had dropped below 10% after 20 days. Plasma luteinizing hormone, having decreased slightly during the first 2 days, was above control values at 5 and 10 days, whereas plasma prolactin did not alter significantly. Ultra- structural changes in lateral prostate epithelium at 24 hr showed dilatation of the endoplasmic reticulum, a decreased number of microvilli, and a virtual absence of secretory granules. The membrane of the basal cells adjacent to the stroma showed increased pinocytotic activity. After 2 days most of the charac- teristics of the control organs were present but there was less secretory activity, the mitochondria were elongated, with a dense matrix, and were confined mainly to apical and basal cell regions. After 5 days many prostatic cells showed concentric whorls of rough endoplasmic reticulum in the Golgi region, with small dense mitochondria predominating in the

upper and lower cell extremities. Changes after 10 days were similar but more marked. The most promi- nent change at 20 days was to relatively undifferen- tiated epithelial cells containing a large nucleus.

Electron microscope microanalysis showed that the presence of Cd in subcellular organelles of the lateral epithelium was associated with the dilatation of the endoplasmic reticulum, loss of secretory granules and reduction in Golgi activity. After 1 day, Cd was demonstrated in the nucleoli and lysosomes of the epithelial cells and in the secretory material in the lumen; after 20 days it was detected only in the nuclei of (new) epithelial cells. Involutionary changes observed at 2, 5 and 10 days were considered to be the result of decreased testosterone levels following Cd-induced testicular injury. Overall, this study indi- cated that the marked ultrastructural changes in the rat lateral prostate correlated with the presence of Cd and were exacerbated by the ensuing hormonal imbalance.

In a related in vitro study, lateral prostate explants from rats were cultured for 6 days with or without added testosterone and/or 10 or lOOrn~-CdCl, (Chandler & Timms, Virchows Arch. Abt. B Zellpath. 1977, 25, 17). Normal epithelium was not maintained in any of these cultures. The epithelial cells became necrotic and were replaced by basal cells which showed varying degrees of differentiation according to the culture conditions. Although incomplete, differ- entiation was most advanced in the testosterone- supplemented cultures; the newly growing cells were cuboid in shape and developed microvilli similar to those in normal tissues but were poorly supplied with endoplasmic reticulum and secretory granules. Cd had a direct effect on the cells, particularly at the higher level, causing necrosis of the basal cells as well as of the original epithelial cells. Differentiation was markedly impaired in the Cd cultures even in the presence of testosterone, although apical microvilli were still observed with the lower Cd level. Cd was shown to be incorporated in both the epithelial and basal cells, becoming located in the nucleus and within cytoplasmic organelles.

In both this and the in uivo study (Timms er al. lot. cit.) investigation of the subcellular distribution of zinc and Cd provided evidence in support of the view that these two elements compete for binding sites within the cells.

Khare et al. (Res. Commun. them. Path. Pharmac. 1978, 20, 351) compared the effects of injecting Cd

Articles of general interest- Fd Cosmer. TO.XICO/. Vol. 17. no. 5 541

or another heavy metal, lead, directly mto the pros- tate of rats. The lead injection (1 mg lead acetate/rat) caused calcification of both bladder and prostate, stromal oedema and excessive periprostatic fibrosis, accompanied in a few cases by stone formation in the bladder. The 1-mg dose of CdCl,, on the other hand, reduced the size and weight of the prostate, and caused marked atrophy of the gland, with formation of cuboidal epithelium and squamous metaplasia in the prostatic acini. While the latter may suggest a progressive precancerous change, no tumour forma- tion occurred in these rats, which were, however, only kept alive for 60 days after treatment. The testes in these Cd-treated rats were small and characterized by almost complete degeneration of the seminiferous tubules, peritubular and interstitial fibrosis and calci- fication of the tubules. There was no evidence of any synergistic effect when lead acetate (0.5 mg) and CdCl, (0.5mg) were injected together into the rat prostate.

As a postscript to these comments on the effects of Cd on the male reproductive system, it is perhaps appropriate to draw attention to the female rat’s rela- tive resistance to this element. Der et al. (ibid 1976 14, 689) found that repeated daily intramuscular injec- tions of 250 pg Cd (as CdCl,) to male rats reduced the size of prostate, testes and epididymis, caused ulcers at the injection site and generally caused more severe reactions and poorer health than occurred in females given similar injections for 54 days. The latter showed some decrease in uterus, ovary and pituitary weights. and in both sexes the liver, spleen and kidneys were enlarged. Males are reported to accumulate more Cd than females under similar conditions of exposure. possibly because of the greater demethylating poten- tial of the female liver.

[P. Cooper-BIBRA]

MORE LIGHT ON PYRROLIZIDINE ALKALOIDS

The natural occurrence and toxic properties of pyr- rolizidine alkaloids have been reviewed extensively before (Cooper, Fd Cosmet. Toxicol. 1974, 12, 559) and a great deal more information is gradually becoming available. Most of the new information concerns the alkaloids of Senecio jacobaea, the rag- wort, and to a lesser extent S. wlgaris, the common groundsel.

Effects on rodents

Significant changes in the histology of the livers, kidneys and lungs of mice have been reported after the feeding of diets containing dried S. jacobaea (Hooper, J. Path. 1974, 113, 227). The powdered plant was fed at a dietary level of 10% for 9 wk and then at 2O”i, for the rest of the experimental period of 193 days. The dried plant contained 0.27% alkaloids, prin- cipally jaconine, jacobine and seneciphylline. Changes in body weight, attributed to the accumulation of ascitic fluid, were seen after day 103. No significant gross lesions were observed in mice killed on days 63 and 129, but those dying or killed on days 1333193 showed ascites, involving fluid volumes of 2-25 ml, and slightly shrunken livers. All livers of mice exam- ined after 129 or more days of feeding showed mega- locytosis of the hepatocytes, cytoplasmic nuclear inva- ginations and cytosegrosomes. Lungs examined after 129 days showed enlarged cells in the bronchial epith- elium, large alveolar cells, and large macrophages with cytoplasmic invaginations. Epithelial cells of the kidney tubules were enlarged in the proximal region and in the loops of Henle.

A relative resistance to the effects of Senecio alka- loids has been observed in rabbits fed 5% dried S.

jacobaea for 90 days and thereafter 10% for up to 263 days (Pierson et al. Res. Commun. them. Path. Pharmac. 1977, 16, 561). Mean total consumption of Senecio was 112.5% of initial body weight. There was no apparent increase in weight, as described in mice and rats, and a slight reduction in body weight was attributed solely to the unpalatability of the feed. Kid-

ney, lung, intestine and myocardium showed no sig- nificant abnormalities, but hepatocytes in all the lobules of the liver appeared to be swollen, causing slight structural distortion. The cytoplasm of the hepatocytes was vacuolated and granular, and the nu- clei were irregular. No fibrosis or bile-duct prolifer- ation was seen. Despite the apparent resistance of this species, a 150-mgkg ip injection of pyrrolizidine alka- loids isolated from S. jacobaea killed two rabbits within 24 hr, suggesting that the low susceptibility of the rabbit to oral administration of these alkaloids is due to poor absorption from the gut.

The effect of the alkaloids of S. jacobaea on liver microsomal mixed-function oxidases in the rat has been investigated by Shull et al. (J. anim. Sci. 1976. 43, 1024). The extracted alkaloids were injected ip in a dose of 65 mg/kg, and the anima!s were killed in batches of five and their livers were prepared for microsomal-activity measurements after 1 and 24 hr and 6 and 57 days. The rate of production of pyrrole metabolites in these preparations reached a peak within 1 hr and then declined and after 24 hr the ac- tivities of aminopyrine N-demethylase and cyto- chrome P-450 were reduced. Microsomal protein was also reduced at 24 hr. These results suggested that metabolically produced pyrroles reacted directly with enzymes to inhibit their own production and had a more delayed effect on N-demethylase activity and cytochrome P-450 either by depressing protein syn- thesis or by increasing protein degradation. In this way, prior exposure to plants containing pyrrolizidine alkaloids may reduce the damage to livestock subse- quently exposed to them again.

The same investigators (Buckmaster et al. ibid 1976. 43, 464) have shown that dietary cysteine gives rats some protection against the toxic effects of pyrrolizi- dine alkaloids. Dried S. jacobaea and S. wiguris con- taining 0.181 and 0.206% total alkaloids, respectively, were fed at a dietary level of 5%. Survival time was shorter with S. vulgaris than with S. jacobaea and the acute ip toxicity of the alkaloids isolated from S. c;u/-