Sublethal lead affects pituitary function of rainbow trout during exogenous vitellogenesis

Sexually maturing female rainbow trout, Oncorhynchus mykiss, were exposed to 10 microg/L of waterborne lead Pb(NO(3))(2) for 12 days during endogenous vitellogenesis and 12 days during exogenous vitellogenesis. Lead had no significant effect on either gonadosomatic indices or mean maximum diameters of developing oocytes during early vitellogenesis. When females were exposed during exogenous vitellogenesis, however, both GSI and oocyte growth were significantly different from controls on day 12. Similarly GSI and oocyte growth was significantly reduced in lead-exposed fish. Atomic absorption spectroscopy measurements of lead levels in liver, ovaries, and blood tissues showed significant levels of lead in the blood. Lead did not accumulate in either the ovaries or the liver. Analysis of pituitary basophils during both endogenous and exogenous vitellogenesis and subsequent comparison with reproductive parameters in the ovaries indicated that GtH-basophils did not significantly increase in controls during endogenous vitellogenesis, and there was no significant change in GSI or ovarian growth in either controls or lead-exposed females. However during exogenous vitellogenesis, control basophils significantly increased over the 12-day experiment, but were not significantly different over 12 days in lead-exposed females. Both GSI and oocyte growth were significantly different from controls in lead-exposed females. The results suggest that naturally occurring changes in GTH-producing basophils during vitellogenesis alters GSI and oocyte growth in female rainbow trout exposed to lead during exogenous vitellogenesis, but not during endogenous vitellogenesis.