Abstract
The incorporation of H3-tyrosine into the protein of the cells in the cortex of rat hair has been investigated by radioautography. In growing hairs, radioactivity is found in the matrix, the upper bulb, and the whole of the keratogenous zone up to the fully keratinized part of the shaft, 10 and 30 minutes after an injection of labelled tyrosine. This is unequivocal evidence of protein synthesis at these sites. There is a very precise relationship between the end of protein synthesis and the hardening of the cortical cells at the top of the keratogenous zone. The way in which the silver grains of the radioautographs are clustered indicates that at 30 minutes after the injection the isotope is distributed more evenly in the matrix and upper bulb than in the top of the keratogenous zone. Possibly this reflects a difference, at these sites, in the cell components engaged in protein synthesis, or in the proteins being synthesized. The fully keratinized and hardened part of the hair was not radioactive at 10 and 30 minutes after the injection of H3-tyrosine. The rate at which the radioactivity moves into this region shows that the hair of rats grows 0.9 mm/24 hours. Comparison of the degree of radioactivity along the growing hair in the 30-minute, 12-hour, and 36-hour materials shows conclusively that protein accumulates in the cortical cells during their keratinization. An injection of a labelled amino acid does not behave as an ideal pulse dose; consequently, the grain density over the hair cortex at 36 hours is 100 per cent larger than would be expected if an ideal pulse dose situation existed.
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Selected References
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- BELANGER L. F. Autoradiographic visualization of the entry and transit of S35 methionine and cystine in the soft and hard tissues of the growing rat. Anat Rec. 1956 Mar;124(3):555–579. doi: 10.1002/ar.1091240305. [DOI] [PubMed] [Google Scholar]
- BIRBECK M. S., MERCER E. H. The electron microscopy of the human hair follicle. I. Introduction and the hair cortex. J Biophys Biochem Cytol. 1957 Mar 25;3(2):203–214. doi: 10.1083/jcb.3.2.203. [DOI] [PMC free article] [PubMed] [Google Scholar]
- BORSOOK H., DEASY C. L., HAAGENSMIT A. J., KEIGHLEY G., LOWY P. H. Metabolism of C14 labeled glycine, L-histidine, L-leucine, and L-lysine. J Biol Chem. 1950 Dec;187(2):839–848. [PubMed] [Google Scholar]
- FLEISCHER S., VIDAVER G., HAUROWITZ F. The rate of incorporation of S35-amino acids into hair protein. J Biol Chem. 1959 Oct;234:2717–2718. [PubMed] [Google Scholar]
- LEBLOND C. P., EVERETT N. B., SIMMONS B. Sites of protein synthesis as shown by radioautography after administration of S35-labelled methionine. Am J Anat. 1957 Sep;101(2):225–271. doi: 10.1002/aja.1001010203. [DOI] [PubMed] [Google Scholar]
- ROGERS G. E. Newer findings on the enzymes and proteins of hair follicles. Ann N Y Acad Sci. 1959 Nov 20;83:408–428. doi: 10.1111/j.1749-6632.1960.tb40916.x. [DOI] [PubMed] [Google Scholar]
- RYDER M. L. Studies of sulphur, phosphorus and some metals in skin follicles. J Histochem Cytochem. 1959 Mar;7(2):133–138. doi: 10.1177/7.2.133. [DOI] [PubMed] [Google Scholar]
- SIMS R. T. ANOTHER VARIABLE TO BE OBSERVED IN AUTORADIOGRAPHS. Nature. 1963 Jul 27;199:395–395. doi: 10.1038/199395a0. [DOI] [PubMed] [Google Scholar]