Spatial expression of the molt-inhibiting horrnone- like gene in the white shrimp Penaeus vannamei

Four IGFBPs have been visualized in striped bass serum. Three appear to be comparable to IGFBP1, -2 and -3 in mammals in terms of their similar molecular weights and regulation by hormones and metabolic status. The fourth (striped bass (sb) IGFBP-4, MW 85-90 kDa) is seen only in adult fish, and has no known mammalian counterpart. Other higher molecular weight bands were also observed, which may represent polymerized forms. In order to evaluate the role of GH in regulating sbIGFBPs, hypophysectomized as well as intact striped bass were injected with GH. In intact fish, ovine growth hormone (oGH) injection at 2pg per gram body weight did not significantly change serum profile of sbIGFBPs, as judged by Western ligand blots, using I human IGF-I as a probe. S-sulfate uptake by ceratobranchial cartilage, however, was stimulated by GH treatment, indicating that the hormone used was biologically active. Hypophysectomy decreased sbIGFBP-3 levels. Injection of oGH at 2pg per gram body weight or tilapia GH at 0.2pg per gram body weight restored sbIGFBP-3 to levels seen in sham-operated fish. oGH also increased somewhat levels of sbIGFBP-4. Changes in sbIGFBP-1 and -2 were either insignificant or inconsistent. Thus, GH may regulate sbIGFBPs in a manner similar although not identical to what has been observed in mammals. Evolutionary conservation of the GH-IGF-IGFBP axis is supported by the present findings. Supported by grants from the California Sea Grant College Program and from Zenyaku Kogyo Co. of Tokyo. Spatial expression of the molt-inhibiting horrnonelike gene in the white shrimp Penaeus vannamei