Serum phosphoprotein phosphorus and calcium levels as reproductive indicators of vitellogenin in highly vitellogenic mature female and estradiol-injected immature rainbow trout (Salmo gairdneri)

Abstract

A linear relationship exists between increasing levels of the indirect indicators serum total phosphoprotein phosphorus (TPP), alkali-labile phosphoprotein phosphorus (ALPP), and total calcium (Ca) and increasing levels of serum vitellogenin (Vg) in mature female rainbow trout (Salmo gairdneri) during active vitellogenesis. A similar result was observed with TPP, Ca, and Vg in immature rainbow trout injected with 17β-estradiol (E₂). Although TPP, ALPP, and Ca could be utilized to distinguish vitellogenic from nonvitellogenic fish, the phosphoprotein phosphorus measures TPP and ALPP emerged as the most reliable indirect indicators of serum Vg levels. Linear regression equations developed from the data allow the estimation of Vg levels from TPP or Ca values for both highly vitellogenic mature female and E₂-injected immature rainbow trout when a direct assay for vitellogenin is not available.