Der Calcium-Spiegel in lebenden und isolierten Muskelfibrillen von Maia Squinado und seine Regulierung durch die sarkoplasmatischen Vesikel

✍ Scribed by Hildegard Portzehl; Peter Zaoralek; Alfons Grieder

• Publisher: Springer
• Year: 1965
• Tongue: English
• Weight: 808 KB
• Volume: 286
• Category: Article
• ISSN: 0031-6768
• DOI: 10.1007/bf00362680

✦ Synopsis

1. The calcium requirement of the enzymatic activity of isolated muscle fibrils of Maia squinado is influenced only slightly by ionic strength between 0,05--0,21 #. At every ionic strength the activity practically disappears when the concentration of free calcium ions G 10 -7 M and reaches a maximum for all ionic strength with a concentration of N 10-5 M.

2. The mechanical activity shows a similar calcium requirement to the ATP splitting when the former is measured by the superpreeipitation of isolated fibrils or by the development of tension of extracted fibres.

3. The degree of shortening of living fibres appears to depend in the same way on the concentration of free calcium ions as the tension development of extracted fibres.

4. The comparison between the calcium requirement found for isolated crab muscles and the reported one of isolated rabbit muscles reveals that the calcium requirement of both species is almost identical. 5. It is also possible to isolate from Maia muscles vesicles which 1. exhibit an "extrasplitting" (HAssELBACK and ~/[AKINOSE 5) after the addition of calcium and 2. diminish the ATPase activity of fibril suspensions to one tenth when they are added to these. This inhibition of ATP splitting is reversed by calcium like the analogous inhibition by vesicles from rabbit muscle. 6. These observations demonstrate that the regulation of the muscular activity is identical in the living Maia fibre and in the glycerol-extracted fibre of the rabbit psoas.

Zusammenfassung. 1. Der Calcium-Bedarf der enzymatischen Aktivit~t isolierter Muskelfibrillen yon Maia Squinado wird yon der Ionenstarke zwischen 0,05 und 0,21 # nur unwesentlich beeinflul3t. Die Aktivitat ist praktisch bei allen Ionenst~rken verschwunden, wenn die freie Calcium-Ionen-Konzentration 10 -7 Mist, nnd sie ist ffir alle Ionenstarken maximal bei einer Calcium-Ionen-Konzentration N 10 5 M.

2. Die mechanische Aktivit~t --gemessen als Superpr~eipitation isolierter Fibrillen oder als Spannungsentwicklung extrahierter Fasern --zeigt einen ahnichen Calcium-Bedarf wie die ATP-Spaltung.