Association between plasma and liver vitamin A levels in the calf; weanling pig, rabbit and rat; and adult goat fed fixed intakes of vitamin A.

To reexamine the relationship between plasma and liver vitamin A levels, data from various species of animals fed fixed intakes of vitamin A ester (expressed as retinol equivalents/kg liver weight/day) were vitamin A ester (expressed as retinol equivalents/kg live weight/day) were studied. The intakes ranging from deficient to toxic were for 48 calves, 4 to 17,600 micrograms; 39 pigs, 17.6 to 19,842 micrograms; 86 rabbits, 4.5 to 287 micrograms; 138 rats, 4 to 16,384 micrograms; and 40 goats, 1 to 17,640 micrograms. Following the feeding of these intakes for periods of between 5 and 133 weeks, blood and liver samples were taken for vitamin A determinations. Plasma vitamin A concentrations reached minimum values at low liver vitamin A levels whereas liver vitamin A levels reached maximum values at high plasma vitamin A concentrations. Upon elimination of data pairs at the extremes, linear regressions of log10 (total liver vitamin A) on plasma vitamin A concentrations and of plasma vitamin A concentrations on log10 (total liver vitamin A) were statistically significant. Therefore it was possible to estimate within limits the log10 (total liver vitamin A) from plasma vitamin A. Applicable limits were for the calf 8 to 46 micrograms/100 ml of plasma, for the pig 14 to 32, for the rabbit 14 to 74, for the rat 5 to 51 and for the goat 22 to 55. Simple correlation coefficients were 0.92, 0.60, 0.93, 0.92 and 0.75.