Quantitative Analysis of Ultrastructural Changes in Developing Rat Cardiac Muscle During Normal Growth and During Acute Volume Load

Nakata, Kazuyasu

doi:10.1253/jcj.41.1237

Cited by 7 publications

(3 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A number of important developmental and physiological events relevant to cardiac growth occur postnatally in rats including increases in myocyte number as well as increases in the subeellular fractions of sarcoplasmic reticulum and contractile proteins (Sasaki, Watanabe, Morishita & Yamagata, 1968;Legato, 1975;Rumyantsev, 1977;Nakata, 1977;Rakusan, 1984). In general, these changes are thought to be complete 2 or 3 weeks after birth.…”

Section: Discussionmentioning

confidence: 99%

Postnatal changes in T‐type calcium current density in rat atrial myocytes.

Best

1992

The Journal of Physiology

View full text Add to dashboard Cite

SUMMARY1. Postnatal changes in Ca2+ current were studied in voltage clamped atrial myocytes isolated from Sprague-Dawley rats. T-and L-type Ca2+ currents were identified using standard electrophysiological and pharmacological techniques. Cells were studied from seven groups of male and six groups of female rats ranging in age from 3 to 14 weeks.2. The density of atrial T-type Ca2+ current showed significant variation during postnatal development, with a maximum density reached at 4 5-5 weeks. At this age, T-current density was 1-44+0±11 pA/pF (n = 23) for cells isolated from male and 1-25 + 0 09 pA/pF (n = 25) for cells isolated from female animals in bathing solutions containing 2 mM-Ca2+. T-current density in atrial cells isolated from younger animals (3'5 weeks postnatal) averaged 1-22 + 0-06 (n = 18) and 1-00 + 0 05 pA/pF (n = 22) or 85 and 80 % of the maximum seen at 4-5-5 weeks for male and female rats, respectively. For rats older than 13 weeks, the average T-current density in atrial cells was 0 50±+003 (n = 18) and 0-51 +0-02 pA/pF (n = 35) or 35 and 41 % of the maximum seen at 4-5-5 weeks for male and female rats, respectively.3. In contrast to the T-type current, the density of atrial L-type Ca2+ current remained unchanged in rats from 3 to 14 weeks old. L-type current averaged 8-2 + 0-2 (n = 134) in male and 7'9+±02 pA/pF (n = 102) in female rats.4. Fluctuation analysis was used to estimate single T-channel current levels in 4 5-and 7-5-week-old male rats. While the T-current density differed by 70% at these two postnatal ages, no significant difference (P > 0 2) in single channel current was found. Single channel current was 0 12 + 0-01 pA (n = 9) for cells from 4-5-week-old and 0 13 + 001 pA (n = 7) for cells from 7-5-week-old rats. Currents were stimulated by test pulses from -80 to -30 mV at 5 mM-Ca2 .5. No postnatal changes were seen in either the kinetics of activation or inactivation of macroscopic T-current. The time to peak current was 9-2 + 0 4 (n = 9) and 9-2 + 05 ms (n = 7) for cells isolated from 4-5-and 7-5-week-old rats, respectively. The time constant of inactivation of current was 21-6 +1 1 (n = 9) and 22-5 + 1-6 ms (n = 7).6. The finding that neither macroscopic current kinetics nor single channel current amplitude varied between cells suggests that the differences in T-current density seen MS 9754 X. XU AND P. M. BEST at different postnatal ages are attributable to a change in channel density rather than a change in single channel conductance or gating.7. T-current density is closely correlated with heart growth rate. For both male and female rats, T-current density is highest during the peak in growth rate that occurs at about postnatal week 5 and lowest when the growth rate approaches zero at adulthood. The maximum T-current density was 15 % higher for cells isolated from male rats (1-44 pA/pF) than those isolated from females (1-25 pA/pF). The maximum growth rate was 34 % higher in the male animals (9-8 g/day) as compared to that for the females (7 3 g/day).8. These results d...

show abstract

Section: Discussionmentioning

confidence: 99%

Postnatal changes in T‐type calcium current density in rat atrial myocytes.

Best

1992

The Journal of Physiology

View full text Add to dashboard Cite

show abstract

“…The differentiation of the cat myocardium may occur for a long period of time from the prenatal stage to 16 days after birth, as compared with the differentia tion of the rat and the guinea pig myocar dium. But we feel that the ultrastructural differentiation of the myocardium at the Ttubule-formation stage is essentially the same in the cat as in the rat and the guinea Pig- Nakata [1977] reported that the increase of volume loads and pressure in the left ven tricle results in the larger cell diameter in the left ventricle than that in the right ventricle. Olivetti et al [1980] also stated that the absolute amounts of cytoplasmic compo nents in ventricular myocytes of the rat were significantly different between the left and right sides at 5 days, but not at either 1 or 11 days after birth.…”

Section: A Trio Ventricular Differentiationmentioning

confidence: 71%

Quantitative Studies on the Ultrastructural Differentiation and Growth of Mammalian Cardiac Muscle Cells

Gotoh¹

1983

Cells Tissues Organs

View full text Add to dashboard Cite

Ultrastructural differentiation of cardiac muscle cells in the bilateral atria and ventricles of the cat at 1, 16, 25 and 40 days and 6 months after birth was studied by morphometry on electron micrographs. At the newborn stage, no T-tubule was found in the ventricular muscle cells, but specific granules were already noted in the atrial myocytes. The cell diameter of the ventricular myocardium was greater than that of the atrium at this stage. The T-tubule was first recognized in the ventricular muscle cells at day 16, at which stage the area occupied by the mitochondria and glycogen in the atrial muscle cells was definitely found to differ from that in the ventricular muscle cells. Thereafter, the differences in the ultrastructure between the atria and ventricles became more remarkable, particularly in the cell diameter and in the mitochondrial area. The cat cardiac muscle cells are characterized by numerous lipid droplets within the cytoplasm in contrast to those of the rat and the guinea pig.

show abstract

“…Pressure volume curves have shown that fetal lamb mayocardium has a much lower compliance than that of the adult [1], This difference in distensibility is believed to be related to the fewer myofibrils and greater water content observed in the myocardium of the newborn [13,14], During the imme diate neonatal period, factors such as the degree of permeability of the ductus arterio sus, levels of pulmonary vascular resistances and systemic arterial pressures could directly or indirectly influence parameters used to evaluate ventricular compliance. For this reason, serial measurements repeated at close intervals are more meaningful than sin gle values representing averaged data gath ered at various postnatal ages [15].…”

Section: Discussionmentioning

confidence: 99%

Left Ventricular Diastolic Function during the First Month of Life

et al. 1988

View full text Add to dashboard Cite

In order to assess possible changes in myocardial relaxation occurring during the neonatal period, M-mode echocardiograms were recorded serially in 9 normal term infants and in another group of 10 one-month-old infants. The tracings were studied with an M-mode calculator. Although individual variations were greater in the data collected during the first 24 h, no significant difference was found in the indices of diastolic function of the left ventricle during the first 4 days of age. The following changes were observed between data recorded at 4 days and 1 month, respectively: normalized peak rate of left ventricle filling, 4.03 vs. 4.71 cm/s; diastolic peak velocity of early posterior motion of aortic root, 1.89 vs. 5.15 cm/s; peak velocity of left ventricle posterior wall motion in diastole, 3.31 vs. 3.50 cm/s; mitral valve EF slope, 59.05 vs. 84.92 mm/s; left ventricle isometric relaxation time, 43.88 vs. 28.50 ms. In conclusion: (1) greater individual variations are observed in indices of left ventricle diastolic function during the first day of life, and (2) significant increase in left ventricle compliance occurs during the first month of life. These changes should play a critical role in the clinical course of newborn with cardiopulmonary disease.

show abstract

Quantitative Analysis of Ultrastructural Changes in Developing Rat Cardiac Muscle During Normal Growth and During Acute Volume Load

Cited by 7 publications

References 18 publications

Postnatal changes in T‐type calcium current density in rat atrial myocytes.

Postnatal changes in T‐type calcium current density in rat atrial myocytes.

Quantitative Studies on the Ultrastructural Differentiation and Growth of Mammalian Cardiac Muscle Cells

Left Ventricular Diastolic Function during the First Month of Life

Contact Info

Product

Resources

About