1. The mechanisms involved in the fine adjustment of iris sphincter muscle tone are largely unknown. The aim of the present study was to clarify the effects of adrenomedullin on the resting tension of the bovine isolated iris sphincter muscle. 2. The motor activity of the bovine isolated iris sphincter muscle was measured isometrically. The effects of adrenomedullin on resting tension were analysed in the presence of indomethacin. The presence of adrenomedullin mRNA in the preparation was determined by reverse transcription-polymerase chain reaction. Immunolabelling for adrenomedullin was also performed. 3. Adrenomedullin significantly decreased the resting tension of the muscle. The relaxant effect of adrenomedullin was significantly inhibited by adrenomedullin (22-52), a putative antagonist for the adrenomedullin receptor, or calcitonin gene-related peptide (CGRP) (8-37), a putative antagonist for the CGRP1 receptor. The relaxant effect was almost completely blocked by a combination of adrenomedullin (22-52) and CGRP (8-37). 4. The relaxant effect of adrenomedullin was also significantly diminished by 2',5'-dideoxyadenosine, an inhibitor of adenylate cyclase, N(G)-nitro-L-arginine, an inhibitor of nitric oxide synthesis, or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, an inhibitor of soluble guanylate cyclase. 5. Reverse transcription-polymerase chain reaction analysis showed that adrenomedullin mRNA was expressed in the muscle strip. Immunopositive staining for adrenomedullin was detected in blood vessel cells and in the iris sphincter muscle cells. 6. These results suggest that adrenomedullin may be an autocrine and paracrine regulator of the resting tension of the iris sphincter muscle. Its biological effects may be due to the direct involvement of adrenomedullin receptors and also to the stimulation of CGRP1 receptors. The stimulation of these receptors by the peptide leads to the activation of adenylate cyclase and soluble guanylate cyclase and subsequent relaxation of the muscle strip.

This study investigated the relationship between eye frailty and physical, social, and psychological/cognitive weaknesses among older adults in Japan. The participants were 192 community-dwelling older adult women. We measured handgrip strength, walking speed, and skeletal muscle mass; additionally, their physical, social, and psychological/cognitive frailties were surveyed using questionnaires. Eye frailty self-checks were used to assess eye frailty. Exploratory and confirmatory factor analyses were employed to verify the validity of the eye frailty self-checks. Eye frailty prevalence and related factors were investigated by conducting a binomial logistic regression analysis, with eye frailty as the dependent variable. The factor analysis results showed that a model could be constructed with the two factors of visual acuity or contrast and visual field. The model’s goodness of fit was acceptable, supporting the validity of the self-checking construct. The Kihon checklist was the only variable with a significant relationship to eye frailty. Regarding the relationship between eye frailty and subordinate items of the Kihon checklist, social withdrawal [odds ratio (OR) 2.437, 95% confidence interval 1.145–5.188], cognitive function (OR 2.047, 95%CI 1.051–3.984), and depressed mood (OR 1.820, 95%CI 1.163–2.848) were significant. Eye frailty can be considered a factor reflecting the existence of social and psychological/cognitive frailties.

Purpose: The purpose of the present study was to clarify the role of Rho-kinase and/or protein kinase C in the resting tension of the isolated pig iris sphincter muscle. Materials and Methods: The motor activity of the isolated pig iris sphincter muscle was measured isometrically. Results: EGTA, a chelator of extracellular Ca 2+ , significantly reduced the resting tension. Y27632, a Rho-kinase inhibitor, significantly reduced the resting tension in a concentration-dependent manner. The resting tension diminished by Y27632 was significantly recovered by the addition of calyculin A, a myosin light chain phosphatase (MLCP) inhibitor, in a concentration-dependent manner. GF109203X, a protein kinase C inhibitor, had no effect on the resting tension. Conclusion: These results suggest that, in the isolated pig iris sphincter muscle, Rho-kinase plays an important role in the generation of spontaneous tone in the resting phase via the inhibition of MLCP activity.

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