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Neuroendocrinology Letters incl. Psychoneuroimmunology & Chronobiology


NeuroendocrinologyİLetters incl. Psychoneuroimmunology & Chronobiology,
ISSNİ0172ñ780X Copyrightİ©İ1998, 1999, 2000, 2001 NeuroendocrinologyİLetters

NEL VOL. 19 No. 4

1998; 19:173-180


Melatonin Retards the Growth of Diethylstilbestrol-Induced Renal Tumors in Male Syrian Hamsters
by Bryant Benson


Chronic diethylstilbestrol (DES) treatment of male Syrian hamsters results in renal carcinoma. Whereas early neoplastic changes occur in the first three to six months of DES treatment, the appearance of frank tumors and metastases appear only after nine or ten months. Our previous work has shown that short photoperiod exposure retards the growth and metastatic spread of DES-induced renal tumors in hamsters. The mechanisms involved in suppression of tumor growth by light deprivation were not determined in these studies, but increased melatonin (MEL) secretion may have played a role. This hypothesis was tested in the present experiment. Young adult, male Syrian hamsters (Lak:LVG) were maintained in long photoperiod (14L:10D). Four groups of animals were established: one group, designated DES, received SC 15 mm Silastic capsules containing 5.0 mg of DES; a second group (DES + MEL) received DES-filled capsules and MEL (0.5 µg/g body wt.) in their drinking water. A control group was given empty Silastic capsules (CON) and another group of controls empty capsules plus MEL (CON + MEL). All capsules were replaced at four month intervals. Subgroups of 12 hamsters from each of the four groups were killed at 3, 6 and 9 months. As expected, DES treatment effected an increase in renal weight, total kidney protein and DNA at 3, 6 and 9 months. The increase in these parameters at 3 and 6 months reflected the observed concomitant interstitial hyperplasia indicative of early neoplastic changes. MEL was without significant effects on body weight, kidney weight, protein and total DNA in the CON + MEL animals. On the other hand, MEL treatment of hamsters that received DES significantly attenuated the effects of DES on kidney weight, kidney protein and total kidney DNA. Tumors were not observed in DES treated until 9 months of treatment, at which time abdominal metastases were also observed. Only two of the 12 hamsters treated with DES + MEL and killed at 9 months showed small tumors on the surface of their kidneys. No indications of metastases were noted in any of the hamsters that received DES + MEL. These results suggest that MEL treatment attenuates the growth of the DES-induced renal adenocarcinoma in male hamsters but whether the effect is via a protective effects on the postulated direct effect of DES on renal cells or results from alterations in neuroendocrine and/or other mechanisms remains to be investigated.

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