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oai:www.ideals.illinois.edu:2142/23416 2023-07-10 col_2142_5131 col_2142_16508 com_2142_5130 com_2142_16507 com_2142_14793 com_2142_8903

Best, Philip M. Xu, Xiao Ping 2011-05-07T14:13:24Z 2011-05-07T14:13:24Z 10000-01-01 1992 Voltage-dependent Ca$\sp{2+}$ currents of cardiac myocytes were studied using patch-clamp techniques. T-type Ca$\sp{2+}$ current density of atrial myocytes was found to be positively correlated with the plasma growth hormone levels and the growth rate of atrial myocytes in normally developing Sprague-Dawley rats, adult Wistar-Furth rats made to reenter an active growth phase following implantation of a growth hormone-secreting tumor, and mutant dwarf rats with retarded growth due to a specific deficiency in pituitary growth hormone synthesis. The voltage and time dependent activation and inactivation of T-type Ca$\sp{2+}$ current are not changed in spite of the changes in T-current density. The unchanged macroscopic current properties and constant single T-channel current suggest that the change in T-current density is likely due to a change in membrane density of T-type Ca$\sp{2+}$ channels rather than a change in the channel protein itself. Though atrial T-current density increases when plasma growth hormone levels are high, it is difficult to prove the involvement of growth hormone in regulating Ca$\sp{2+}$ channel expression because of the complication from other hormones and growth factors. It is also possible that the correlation between atrial T-current density and plasma growth hormone levels is merely accidental. The up-regulation of T-type Ca$\sp{2+}$ channel density during active growth is specific for atrial myocytes, since T-type Ca$\sp{2+}$ current is not induced in ventricular myocytes from the tumor-bearing rats. High T-current density during the period of active growth of atrial myocytes supports the idea that T-type Ca$\sp{2+}$ channels may have some role in embryonic/postnatal development in certain tissues. L-type Ca$\sp{2+}$ channels are regulated in a different way. In contrast to T-type Ca$\sp{2+}$ current, L-type Ca$\sp{2+}$ current density remains constant in both atrial and ventricular cells from rats during either normal postnatal development in young rats or induced active growth in adult rats bearing growth hormone-secreting tumors. The constant L-current density may be important to keep up Ca$\sp{2+}$ influx with increased cell size to support normal cardiac contraction. Made available in DSpace on 2011-05-07T14:13:24Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9215913.pdf: 4348605 bytes, checksum: f289efa7e92137c370193a2d6fb50567 (MD5) Previous issue date: 1992 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T15:04:20Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:30:43-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission ETDs are only available to UIUC Users without author permission U of I Only AAI9215913 (UMI)AAI9215913 http://hdl.handle.net/2142/23416 eng Copyright 1992 Xu, Xiao Ping Biology, Animal Physiology Modulation of calcium channel expression in cardiac myocytes of rats during growth hormone-induced growth or normal postnatal development text Physiology Physiology University of Illinois at Urbana-Champaign Dissertation Ph.D.