Objective: Somatotropinomae are classified as densely and sparsely granulated adenomae, which typically exhibit a perinuclear pattern (PP) and a dot pattern (DP) in cytokeratin (CK) immunostaining respectively. Some exhibit a mixed pattern (MP). We studied the relationship between these somatotropinoma subtypes and their clinico-pathological features. Methods: The study population consisted of 141 Japanese acromegalic patients. We evaluated their clinical presentation and their response to provocation tests with TRH and LHRH and to suppression (octreotide) test. Tumour tissues were subjected to immunostaining for CAM-5.2, MIB-1, CD34, E-cadherin (CDH1) and p53 (TP53). In 43 cases (30 non-DP and 13 DP), we analysed gsp mutations (constitutively activating mutations of the G s a protein that is encoded by GNAS gene). Results: The 141 adenomae were categorised into three subtypes based on their CK staining patterns; 30 (21.3%) exhibited DP, 83 (58.9%) exhibited PP, and 28 (19.9%) exhibited MP. Compared with the other subtypes, DP adenomae were significantly larger, and their E-cadherin expression and response to TRH, LHRH and octreotide challenge were lower. The postoperative cure rate tended to be lower in DP adenomae. gsp mutations were detected in 25 of 43 cases examined (58.1%); 20 of the 30 non-DP (66.7%) and 5 of the 13 DP tumours (38.5%) were affected by the mutation. Conclusion: DP somatotropinomae exhibit characteristic features. Compared with the non-DP subtypes, DP adenomae manifested a larger tumour size, a lower incidence of abnormal responses to TRH and LHRH challenge, a poor response to octreotide test and a lower expression of E-cadherin. gsp mutation was not exclusive for non-DP somatotropinomae.

We conclude that the prevalence of gsp mutations in Japanese acromegaly patients is comparable to those of other reports from various regions. Therefore, Japanese patients do not stand as an example for geographical or racial difference in the prevalence of gsp mutations in GH-secreting pituitary adenomas.

Somatostatin (somatotrophin release-inhibiting factor, SRIF), a fourteen amino acid peptide, was discovered in the hypothalamus (Brazeau et al. 1973). This peptide was shown to inhibit the secretion of growth hormone in the hypophysis (Brazeau et al. 1973). Later, SRIF was shown to be widely distributed in the brain, and it is now known to be an important neurotransmitter in the brain. The locus coeruleus, a pair of small nuclei located in the brainstem, consists of tightly packed noradrenergic neurones which project to virtually the entire brain and spinal cord. Hence, this nucleus, as the main supplier of noradrenaline in the brain, plays a vital role in brain function. SRIF inhibits locus coeruleus neurones by activating an inward rectifier K¤ current, and this SRIF effect is mediated through a pertussis toxin (PTX)-sensitive G protein (Inoue, Nakajima & Nakajima, 1988). However, the type (or types) of PTX-sensitive G protein (Gi1, Gi2, Gi3 or Gï) involved in this SRIF effect has yet to be determined. In AtT-20 cells (a mouse pituitary tumour cell line) and in human pituitary tumour cells, SRIF activates an inward rectifier K¤ current, and this SRIF effect is also mediated by a PTX-sensitive G protein (Yamashita, Shibuya & Ogata, 1988;Pennefather, Heisler & MacDonald, 1988;Kozasa, Kaziro, Ohtsuka, Grigg, Nakajima & Nakajima, 1996). In AtT-20 cells as well, it has not yet been determined which one of several PTX-sensitive G proteins is involved in the SRIF effect. The objective of this paper is to identify the G protein that mediates the SRIF effect on inward rectifier K¤ currents in locus coeruleus neurones and in 1. Types of G proteins (G protein á_subunit subtypes) which mediate the activation of inward rectifier K¤ currents by somatostatin (somatotrophin release-inhibiting factor, SRIF) were determined in cultured locus coeruleus neurones from newborn rats and in AtT-20 cells (a mouse pituitary cell line). 2. The whole-cell patch clamp technique was used together with injection of antibodies against pertussis toxin (PTX)-sensitive G protein á_subunits or with injection of antisense (or sense) oligonucleotides against these G proteins. 3. In locus coeruleus neurones, the SRIF-induced activation of inward rectifier K¤ currents was inhibited by anti-Gái1ÏGái2 antibody injection, but not by anti-Gái3 or by anti-GáïÏGái3 antibody injection, suggesting that the SRIF response is mediated through Gái1 andÏor Gái2. 4. The SRIF-induced activation of the inward rectifier was suppressed in locus coeruleus neurones after injection of antisense oligonucleotides against Gái2, but not by injection of sense oligonucleotides against Gái2. Injection of antisense (or sense) oligonucleotides against Gái1, Gái3 and Gáï(common) had no effect. These results suggest that Gái2 is involved in this SRIF response. 5. In AtT-20 cells, the SRIF-induced activation of inward rectifier K¤ currents was suppressed by injection of anti-Gái3 antibody, but not by injection of anti-Gái1ÏGái2 antibody. 6. The above results indicate that Gé medi...

1. Substance P (SP) induces a slow neuronal excitation in cholinergic neurons from the nucleus basalis by suppressing an inwardly rectifying K+ current (Kir). We have determined which G protein alpha-subunit mediates this SP effect. 2. After intracellularly injecting antibody against each alpha-subunit of G proteins (Gq alpha/11 alpha, G12 alpha, and G13 alpha) with an Eppendorf microinjector, we examined, by using the whole cell patch-clamp and the ON-cell mode of single-channel recording, the effect of SP on Kir in cultured neurons of the nucleus basalis. The effect of SP on Kir was substantially reduced in neurons injected with antibodies to Gq alpha/11 alpha but not with antibodies to G12 alpha or G13 alpha. 3. The effects of antibodies against three isozymes of phospholipase C (PLC-beta 1, PLC-beta 2, and PLC-beta 3) were tested. The SP-induced suppression of Kir was reduced by antibody against PLC-beta 1 but not by antibodies against PLC-beta 2 or PLC-beta 3. 4. We conclude that the SP-induced inhibition of Kir in nucleus basalis neurons is mediated by Gq/11 and PLC-beta 1.