The intra‐embryonic and extra‐embryonic distribution of hydroxyproline in the hen's egg

Abstract

AbstractRecent modifications in the biochemical method for determining hydroxyproline have improved its accuracy. The increasing use of fibroblasts from chick embryos for production of collagen necessitates the reinvestigation of hydroxyproline production in chick embryos. The levels of proline and free and bound hydroxyproline were determined in embryonated hen eggs by the method of Prockop and Udenfriend. Determinations on the yolk, white, and embryo were done separately. Analysis of specimens taken from the onset of incubation to the thirteenth day of incubation revealed the presence of 20 to 80 μMoles of proline in each compartment throughout the period of study. Free hydroxyproline was present in the yolk and white at a constant low level of less than 1 μMole per egg. Hydroxyproline (total: bound and free) was first detected in five day embryos. By nine days the level was 0.5 μMoles; at 11 days, 1.5 μMoles, and at 13 days, 4.25 μMoles. The increase in hydroxyproline when calculated per milligram of wet weight of embryo approximated a straight line.