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Effect of ryanodine on myocardial calcium (1975)

Frank, Martin ; Sleator, William W.

Springer

Naunyn-Schmiedeberg's archives of pharmacology 290 (1975), S. 35-47

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ISSN: 1432-1912

Keywords: Guinea Pig Atrial Muscle ; Ryanodine ; Ryanodine Steady-State Condition ; Post-Rest Potentiation ; Calcium Exchange

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine

Notes: Summary The effects of ryanodine and ryanodine steady-state condition (RSSC) on contractile-related calcium were examined in isolated guinea pig left atrial muscle. 1. RSSC is a specific irreversible condition occurring after a brief exposure to 1×10−7 M ryanodine, followed by washing. It is characterized by elimination of the contraction following a 10-sec rest interval (post-rest) and prolongation of the associated action potential duration (AP50%) from 78.9 to 160.8 msec with minimal alteration in steady-state tension development determined at 1 Hz. 2. Induction of RSSC with a ryanodine-bovine serum albumin conjugate produced similar alterations in post-rest contractile strength and action potential duration. 3. In the presence of 1×10−7 M ryanodine, guinea pig left atria exhibit a significant increase in total 45Ca efflux from two rapidly exchangeable compartments (compartment 1, t 1/2=1.58 min; compartment 2, t 1/2-8.20 min). 4. In atria loaded after the induction of RSSC, total 45Ca release was significantly reduced by 7.2% of the total exchange. 5. The 45Ca exchange space for RSSC atria was reduced from 23.22±0.81 to 19.85±1.22 ml per 100 g muscle without a significant reduction in the total exchange space. 6. From these results, it is concluded that the effects of low concentrations of ryanodine and RSSC are to alter the contractile calcium levels of the tissue, primarily from sarcolemmal membrane sites which regulate post-rest contractile strength and action potential duration.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00499988

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EPR and ENDOR study of chiral nitroxides (1989)

Stegmann, Hartmut B. ; Schaber, Frank-Martin ; Schuler, Paul ; [et al.]

Chichester : Wiley-Blackwell

Organic Magnetic Resonance 27 (1989), S. 887-891

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ISSN: 0749-1581

Keywords: EPR ; ENDOR ; Chiral nitroxides ; Restricted rotation ; Chiral recognition ; Chemistry ; Analytical Chemistry and Spectroscopy

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Racemic and achiral alkyl aryl nitroxides were examined at various temperatures. The restricted rotation of the aminoxyl substituents was indicated both by the β-proton coupling constants and by the inequivalence of the aromatic ortho protons. These results are interpreted by the presence of two different rotamers which may lead to two splitting constants for the β-proton. The capability for inter- and intra-molecular hydrogen bond formation in the nitroxides investigated was demonstrated. However, complexes consisting of chiral radicals and chiral auxiliaries do not show hyperfine structures which unambiguously indicate diastereomeric species. Therefore, hydrogen bonding between chiral molecules is not sufficient for chiral recognition if an alteration of the hyperconjugation angle does not occur. Simple steric interactions can result in the doubling of the β-proton coupling constant, independently of diastereomeric complex formation.

Additional Material: 2 Ill.