ABSTRACT
Various polypeptide hormones including vasopressin (VP) and gastrin-releasing peptide (GRP) are produced by small cell lung carcinomas (SCLC). VP as well as GRP have mitogenic effects on several cell types and are proposed to be autocrine growth factors. In this study the presence of VP mRNA, oxytocin (OT) mRNA and GRP mRNA was investigated in cell lines derived from SCLCs. Out of 26 cell lines 3 contained low amounts of VP mRNA (GLC-8, SCLC-21H and NCI-H345) and 7 contained abundant GRP mRNA (GLC-16, GLC-1-M13, SCLC-22H, NCI-H249, NCI-H345, NCI-H449 and NCI-H450). The GRP mRNA-containing cell lines belong to the classic SCLC type, whereas VP mRNA was found in two classic and one variant cell line. None of the SCLC cell lines contained detectable levels of OT mRNA. Of the three VP-expressing SCLC cell lines, GLC-8 had the highest level of VP mRNA. Both the length of the transcript and the hybridization with different probes containing exons A and C of the VP gene suggest that the detected transcript is a normal VP messenger. SCLC GLC-8 contained low levels of VP immunoreactivity and VP receptors. In GLC-8 an autocrine role of VP may be suspected.
Subject(s)
Carcinoma, Small Cell/metabolism , Gene Expression Regulation, Neoplastic , Lung Neoplasms/metabolism , Peptide Biosynthesis , Vasopressins/biosynthesis , Base Sequence , Blotting, Northern , Carcinoma, Small Cell/genetics , Carcinoma, Small Cell/pathology , DNA Probes , Gastrin-Releasing Peptide , Humans , Lung Neoplasms/genetics , Lung Neoplasms/pathology , Molecular Sequence Data , Oxytocin/biosynthesis , Oxytocin/genetics , Peptides/genetics , RNA, Messenger/analysis , RNA, Neoplasm/analysis , Tumor Cells, Cultured/metabolism , Vasopressins/geneticsABSTRACT
Abstract The aim of this study was to characterize neurohypophyseal hormone receptors in the brain of the canary (Serinus canarius) by using autoradiographical and biochemical procedures with a radioiodinated vasotocin analogue, [(125) l]d(CH(2))(5)[Tyr(Me)(2), Thr(4), Orn(8), Tyr-NH(2) (9)]vasotocin ([(125) I]-OTA). This synthetic analogue was used previously to identify a population of oxytocin-like receptors in the rat brain that have high affinity for vasotocin. In vitro autoradiography revealed high affinity binding sites for [(125) I]-OTA in the canary brain in the archistriatum surrounding the nucleus robustus archistriatalis. Scatchard analysis of [(125) I]-OTA binding to a synaptic membrane fraction prepared from the archistriatal region including the nucleus robustus archistriatalis indicated the presence of a single population of binding sites (K(d)= 0.05 nM; B(max)= 4 fmol/mg protein). Displacement studies revealed that the order of potency of certain peptides to inhibit [(125) I]-OTA binding was as follows: vasotocin (K(i)= 0.4 nM) > oxytocin = vasopressin > mesotocin (K(i)= 8.0 nM). The administration of testosterone to female canaries did not affect [(125) I]-OTA labelling in the archistriatum detected by autoradiography and did not influence [(125) I]-OTA binding constants in the membrane binding assay. In conclusion, this study provides morphological and biochemical evidence of a vasotocin-target site in the archistriatum in close association with the central vocal control circuit in the canary brain.
