Uptake and Distribution of Cobalt in Rat Ovaries and Pituitary: Acute Effects of Cobalt on Preovulatory Luteinizing Hormone, Follicle Stimulating Hormone, Prolactin and Progesterone Levels, and on Ovulation in Rats

Katalin Paksy1, Ferenc Olajos2, Béla E. Tóth3, Miklós Náray1, Erzsébet Tátrai1, and László Huszár1

1 National Institute of Chemical Safety, Fodor József National Center for Public Health, Budapest, Hungary
2 Department of Obstetrics and Gynecology, Semmelweis Medical University, Budapest, Hungary
3 Department of Human Morphology and Developmental Biology, Semmelweis Medical University, Budapest, Hungary

Corresponding author: Katalin Paksy, Ph.D.
    Department of Reproductive Toxicology
    National Institute of Chemical Safety
    Fodor József National Center for Public Health,
    P.O. Box 36, H-1450 Budapest, Hungary
    Telephone: (+36) 1 215 7890
    Fax number: (+36) 1 215 9044
    E-mail: arkai@sparc.core.hu

CEJOEM 1999, Vol.5. No.3-4.:313-323

Key words:
Co2+, gonadotrop hormones, pituitary, ovulation inhibition, reproductive toxicity, steroidogenesis
 
Abstract:
Cobalt sulphate (CoSO4, 40, 60 or 80 mg/kg bw sc) was given to Sprague-Dawley (SPRD) rats on diestrus II of the cycle. On the following estrus, oocytes were counted, pituitary and ovaries were examined for histopathology. Cobalt content of pituitary, ovary and blood was determined by atomic absorption spectrophotometry. In a second group of rats proestrous levels of Luteinizing Hormone (LH), Follicle Stimulating ormone (FSH), and Prolactin (PRL) in serum and pituitary, and serum progesterone (P) levels were determined by radioimmunoassay.
    Cobalt accumulated in the pituitary, luteal and nonluteal tissues. CoSO4 was able to block ovulation in 5.9%, 30.4% and 76.7% at doses 40, 60 or 80 mg/kg bw, respectively. At 60 mg/kg CoSO4, in proestrous rats' serum LH levels failed to rise, P levels elevated, though they remained lower than in controls. At the same time LH content of the pituitary increased. FSH and PRL levels of serum and pituitary remained unaltered. No histopathological changes of the ovary or pituitary were observed. In conclusion, CoSO4 proved to be able to modulate ovarian function. The lack of histological alteration and the maintained steroidogenic capacity in the ovary indicate that cobalt acts via interfering with the regulatory function of the hypothalamic-hypophyseal axis. Because treatment related decrease in serum LH levels was accompanied by higher pituitary LH content, rather the release than the synthesis or storage might be influenced by cobalt. Since no influence on FSH and PRL levels was detected the specificity of cobalt effect on LH release is to be considered.

Received:  24 August 1999
Accepted:  01 September 1999
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