GROWTH HORMONE- AND PROLACTIN-LIKE PROTEINS OF THE 



BLUE SHARK {PRION ACE GLAUCA) 



U. J. Lewis\ R. N. p. Singh% B. K. Seavey\ R. Lasker=, and Grace E. Pickford' 



ABSTRACT 



The two major disc-electrophoretic components, designated as "slow" and "fast," 

 which are seen in fresh homogenates of the pars distalis of the blue shark (Prionace 

 glauca) pituitary gland were isolated. Some alteration of the proteins occurred during 

 the purification as evidenced by appearance of a slightly faster migrating band in each. 

 The slow component and its altered form had a molecular weight of 22,000 daltons ; the 

 fast, and its modified form, 20,000 daltons. The two proteins were very similar chem- 

 ically and immunologically, but definite differences were noted. Both gave a precipitin 

 line with antiserum to mouse growth hormone, although quantitatively different, but 

 neither reacted to antiserum to mouse prolactin. The peptide maps of the two proteins 

 were identical except for three peptides. Both contained two moles of tryptophan and 

 six half-cystine residues. These results indicate that the pars distalis of the blue shark 

 contains two very similar proteins that resemble both growth hormone and prolactin of 

 mammals. 



There have been few reports that have dealt 

 with the isolation of purified preparations of 

 growth hormone and prolactin from pituitary 

 glands of fish. This most probably stems from 

 the fact that there is no convenient bioassay for 

 these piscine hormones. Wilhelmi (1955) pur- 

 ified growth hormone from the hake; Donaldson, 

 Yamazaki, and Clarke (1968) reported on pro- 

 lactin of salmon; and Emmart and Bates (1968) 

 described purification of prolactin of the pollack. 

 As a means of circumventing bioassays, we 

 thought that disc electrophoresis might prove 

 successful. The method has been used by us to 

 follow the purification of growth hormone and 

 prolactin of the mouse (Cheever, Seavey, and 

 Lewis, 1969), human (Lewis, Singh, and Seav- 

 ey, 1971), and turtle (Singh, Seavey, and Lewis, 

 1972).' The approach appeared even more rea- 



^ Division of Endocrinology, Scripps Clinic and Re- 

 search Foundation, La Jolla, CA 92037. 



° National Marine Fisheries Service, Southwest Fish- 

 eries Center, La Jolla, CA 92037. 



° Department of Biology, Hiram College, Hiram, OH 

 44234. 



* Singh, R. N. P., B. K. Seavey, and U. J. Lewis. 

 1972. Purification and some properties of growth hor- 

 mone and prolactin of the turtle. (Manuscr.) 



Manuscript accepted March 1972. 



FISHERY BULLETIN: VOL. 70, NO. 3, 1972. 



sonable for the isolation of the shark hormones 

 when we found that the electrophoretic pattern 

 of the pars distalis extract contained only two 

 major bands. This has been found to be the 

 case for many species, and growth hormone 

 usually has been identified as the slower mi- 

 grating of the two bands (Nagy, Kurz, and 

 Baranyai, 1969; Nicoll and Nichols, 1971; Nicoll 

 and Licht, 1971) . An exception to this has been 

 found in the human (Friesen, Guyda, and 

 Hardy, 1970; Lewis et al., 1971) where growth 

 hormone is more acidic than prolactin and, there- 

 fore, migrates more rapidly during electrophor- 

 esis at an alkaline pH. 



Making the assumption, then, that the two 

 major bands seen in the electrophoretic pattern 

 of the shark pituitary extract were growth hor- 

 mone and prolactin, we devised a procedure for 

 their isolation and used electrophoresis as a 

 means of following the purification. The iso- 

 lation procedure and some properties of the pur- 

 ified proteins are described in this communica- 

 tion. 



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