GROWTH-PATTERNS IN SELECTED ORGANS OF THE MINIATURE SWINE AS DETERMINED BY GROSS MACROMOLECULAR-COMPOSITION

As part of a larger study designed to characterize the early developme ntal stages of the Hormel-Hanford strain miniature pig, the brain, kid ney, liver, pancreas, and spleen from male animals were examined for c hanges in RNA, DNA, and protein contents from 1 to 196 d after birth. Distinct patterns were found for changes with age in macromolecular le vels. Protein levels increased from d 1 to 56 in all organs except spl een, in which little change was noted. Gel electrophoresis showed litt le qualitative change in the liver protein profile during this period. A fat-free, non-nucleic acid, protein-containing fraction, insoluble in hot alkali, appeared in the brain after approximately 1 wk followin g birth. DNA concentrations decreased markedly from d 1 to d 196 for b rain, kidney, and spleen but decreased more gradually for liver and pa ncreas. RNA levels declined slightly or remained the same in all organ s except pancreas, where a large increase occurred from d 1 to weaning (56 d). Growth proceeded in all organs by increases in cell number (h yperplasia), as evidenced by increases in total (level or concentratio n x organ weight) DNA, or by hypertrophy, as evidenced by increases in the ratio of protein to DNA or by a combination of both processes. Hy pertrophic growth was attained by d 56 and continued to sexual maturit y in all organs except spleen. Hyperplastic growth continued to sexual maturity in all organs except brain.