Der Einflu� von Sexualsteroiden auf die isometrische Kontraktion des isolierten Rattenzwerchfells

Abstract

The influence of estradiolbenzoate, hydroprogesteroncapronate and pregnancy on the mechanical reaction of the directly and indirectly stimulated nerve-diaphragm preparation has been the subject of this investigation. Rats were ovario-ectomized and the hormone preparations were injected subcutaneously. After a lapse of 9 days the test preparation was made. 1. Estrogen and the estrogen-gestagen combination have a similar effect on the isometric contraction of the transversely striated muscle. The times of rising and relaxation were prolonged after indirect and direct stimulation. The contraction amplitude had not altered compared to the control group. 2. Gestagens and the hormone situation of pregnancy entail, independent of the kind of stimulation, a decrease of the tension progress and the speed of the tension increase. The gestagen-treated animals underwent a shortened contraction process. These findings enable us to comment on the different efficiencies of women during various cycle phases and during pregnancy.

Effects of ovariectomy and hindlimb unloading on skeletal muscle

“…In the present study, TPT in EDL and RT 1/2 for all four muscles examined were slower in Int than in Ovx animals. This pattern supports the previous finding of extended relaxation times in diaphragm in frog muscle fibers after treatment with diethylstilbestrol (a synthetic estrogen), in human quadriceps during the ovulatory phase of the menstrual cycle (22), and in diaphragm of OvxϩE 2 rats compared with Ovx animals (12). The estrogen-related increase in muscle relaxation times in the present study cannot be explained by differences in fiber type and suggests an effect of estrogen on the sarcoplasmic reticulum (SR).…”

“…In the present study, the effects of ovariectomy on specific tension (P o /muscle mass) were inconsistent. In an earlier study on rat diaphragm, specific tension was similar in Ovx rats, Ovx rats replaced with estrogen (OvxϩE 2 ), and OvxϩE 2 rats that were also given progesterone (12). However, specific tension was significantly lower in Ovx rats given only progesterone (12).…”

“…In an earlier study on rat diaphragm, specific tension was similar in Ovx rats, Ovx rats replaced with estrogen (OvxϩE 2 ), and OvxϩE 2 rats that were also given progesterone (12). However, specific tension was significantly lower in Ovx rats given only progesterone (12). In humans, specific tension in the adductor pollicis muscle was found to be higher in premenopausal than in postmenopausal women (17).…”

Sex hormone-mediated change on muscle activation deactivation dynamics in young eumenorrheic women

“…Examinations involving a combined treatment of estrogen and progesterone are scarce and show conflicting results. Combined estradiol-progesterone treatment on OVX animals showed no effect on peak tension compared to OVX animals (Horner and Lehmann, 1978). Schneider et al, however, reported that OVX + E + P animals have a significantly higher isometric peak force compared to OVX animals (Schneider et al, 2004).…”

“…It has been reported, however, that estradiol-deprived mice exhibit a lower peak tension (Collins et al, 2018), suggesting that estradiol has beneficial effects on force production, presumably due to the enhancement of muscle's regulatory light chain phosphorylation (Stull et al, 2011;Lai and Lowe, 2013), an increase in the accessibility of actin-binding (Levine et al, 1998), or maintenance of muscle MyHC composition (Kadi et al, 2002). On the other hand, OVX animals treated with progesterone only had significantly lower specific tension (peak force/muscle mass) compared to OVX animals (Horner and Lehmann, 1978). Data in animal models on the effect of progesterone alone on time to peak torque is lacking.…”