Mild renal hypertension alters run training effects on the frequency response of rat cardiomyocyte mechanics

We examined the effects of run training on the frequency dependence of cardiomyocyte mechanics and intracellular calcium concentration ([Ca2+]i) dynamics in rats with mild renal hypertension. Male Fischer 344 rats aged 2–3 mo underwent a sham operation or stenosis of the left renal artery, which increased systolic blood pressure 20–30 mmHg. Half of the rats in each group underwent treadmill run training for >16 wk. Isolated cardiomyocytes were paced at 1.0 and 0.2 Hz in 2 mM external Ca2+ concentration at 29°C. Under these conditions, negative frequency responses, i.e., decreased value with increased frequency, were recorded for peak shortening, shortening velocity, and the integral of the [Ca2+]i transient in both groups. Run training amplified the negative frequency response for the integral of the [Ca2+]i transient in both groups, but it amplified the negative frequency response for the shortening dynamics only in the normotensive sham-operated and not in the hypertensive rats. These results, as well as others for relaxation parameters, suggest that renal hypertension altered the effects of run training on the frequency response for cardiomyocyte contractile apparatus and/or passive mechanical properties, which respond to [Ca2+]i.

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Renal hypertension prevents run training modification of cardiomyocyte diastolic Ca2+ regulation in male rats

Journal of Applied Physiology ◽

10.1152/jappl.2001.90.6.2063 ◽

2001 ◽

Vol 90 (6) ◽

pp. 2063-2069 ◽

Cited By ~ 12

Author(s):

Bradley M. Palmer ◽

Joshua M. Lynch ◽

Steven M. Snyder ◽

Russell L. Moore

Keyword(s):

Renal Hypertension ◽

Left Ventricular ◽

Male Rats ◽

Left Renal Artery ◽

Sham Operation ◽

Fischer 344 Rats ◽

Efflux Rate ◽

Fischer 344 ◽

Regulation Mechanisms ◽

Electrical Pacing

The combined effects of endurance run training and renal hypertension on cytosolic Ca2+ concentration ([Ca2+]c) dynamics and Na+-dependent Ca2+ regulation in rat left ventricular cardiomyocytes were examined. Male Fischer 344 rats underwent stenosis of the left renal artery [hypertensive (Ht), n = 18] or a sham operation [normotensive (Nt), n = 20]. One-half of the rats from each group were treadmill trained for >16 wk. Cardiomyocyte fura 2 fluorescence ratio transients were recorded for 7 min during electrical pacing at 0.5 Hz, 2 mM extracellular Ca2+ concentration, and 29°C. The rate of [Ca2+]c decline was not changed by run training in the Nt group but was reduced in the Ht group. At 7 min, cardiomyocytes were exposed to 10 mM caffeine in the absence of Na+ and Ca2+, which triggered sarcoplasmic reticular Ca2+ release and suppressed Ca2+efflux via Na+/Ca2+ exchanger. External Na+ was then added, and Na+-dependent Ca2+ efflux rate was recorded. Treadmill training significantly enhanced Na+-dependent Ca2+efflux rate under these conditions in the Nt group but not in the Ht group. These data provide evidence that renal hypertension prevents the normal run training-induced modifications in diastolic [Ca2+]c regulation mechanisms, including Na+/Ca2+ exchanger.

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Age-related increases in diaphragmatic maximal shortening velocity

Journal of Applied Physiology ◽

10.1152/jappl.1996.80.2.445 ◽

1996 ◽

Vol 80 (2) ◽

pp. 445-451 ◽

Cited By ~ 18

Author(s):

S. K. Powers ◽

D. Criswell ◽

R. A. Herb ◽

H. Demirel ◽

S. Dodd

Keyword(s):

Force Production ◽

Specific Force ◽

Fischer 344 Rats ◽

Rat Diaphragm ◽

Shortening Velocity ◽

Fischer 344 ◽

Age Related ◽

Highly Correlated ◽

Related Increase

Recent evidence demonstrates that aging results in an increase in fast (type IIB) myosin heavy chain (MHC) in the rat diaphragm. It is unknown whether this age-related change in fast MHC influences the diaphragmatic maximal shortening velocity (Vmax). Therefore, we tested the hypothesis that aging is associated with an increase in the diaphragmatic Vmax and that the increase in the Vmax is highly correlated with the percentage of type IIb MHC. In vitro contractile properties were measured with costal diaphragm strips obtained from young (4 mo old; n = 8) and (old 24 mo old; n = 8) male Fischer-344 rats. Diaphragmatic maximal tetanic specific force production was 14.5% lower in the old compared with the young animals (23.0 +/- 0.4 vs. 19.7 +/- 0.8 N/cm2; P < 0.05). In contrast, the diaphragmatic Vmax was significantly higher in the old compared with the young animals (5.5 +/- 0.1 vs. 4.4 +/- 0.3 lengths/s; P < 0.05). Although the percent type IIb MHC was significantly higher (approximately +14%; P < 0.05) in the old compared with the young animals, the correlation between Vmax and percent type IIb MHC was relatively low (r = 0.50; P = 0.05). These data support the hypothesis that an age-related increase in diaphragmatic Vmax occurs; however, factors in addition to type IIb MHC are involved in regulating diaphragmatic Vmax. Interestingly, although aging resulted in a decrease in diaphragmatic maximal specific force production, power output at all muscle loads was maintained in the old animals due to the increase in diaphragmatic shortening velocity.

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Long-term vascular access in the rat: importance of asepsis

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1981.241.4.h606 ◽

1981 ◽

Vol 241 (4) ◽

pp. H606-H612 ◽

Cited By ~ 5

Author(s):

M. B. Popp ◽

M. F. Brennan

Keyword(s):

Superior Vena ◽

Experimental Studies ◽

Vena Cava ◽

Sham Operation ◽

Fischer 344 Rats ◽

Fischer 344 ◽

Catheter Infection ◽

Catheterization Technique ◽

Vascular Catheters

Chronic indwelling vascular catheters have been used in the rat for many types of experimental studies. Most experiments have been of short duration with little attention to aseptic technique during catheter placement. In this study, rats subjected to a sterile superior vena cava (SVC) catheterization technique, a convential clean but nonsterile SVC catheterization technique, or sham operation were compared. Male Fischer 344 rats (wt 175-200 g) were catheterized or sham operated and then received food and water ad libitum for 25 days. At time of spontaneous death or being killed the SVC was examined grossly and microscopically for infection. Three of six nonsterile conventionally catheterized animals died, and five of these six animals had infected catheters. All sterilely catheterized and sham-operated rats lived 25 days, and none had catheter infection. Sterilely catheterized rats gained weight (1.9 g/day), were in positive nitrogen balance, and had organ weight and blood studies similar to sham-operated noncatheterized controls. Nonsterile catheterization resulted in catheter infection such that normal physiological studies would be uninterpretable.

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Toxic effects of inhaled DMMP on the kidneys of Fischer-344 rats

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100128687 ◽

1987 ◽

Vol 45 ◽

pp. 880-881

Author(s):

D.R. Mattie ◽

C.J. Hixson

Keyword(s):

Left Kidney ◽

Inhalation Exposure ◽

Electron Microscopic Examination ◽

Exposure Period ◽

Male Rats ◽

Continuous Exposure ◽

Fischer 344 Rats ◽

Electron Microscopic ◽

Thin Sections ◽

Fischer 344

Dimethylmethylphosphonate (DMMP) is a simple organophosphate used industrially as a flame retardant and to lower viscosity in polyester and epoxy resins. The military considered the use of DMMP as a nerve gas simulant. Since military use of DMMP involved exposure by inhalation, there was a need for a subchronic inhalation exposure to DMMP to fully investigate its toxic potential.Male Fischer-344 rats were exposed to 25 ppm or 250 ppm DMMP vapor on a continuous basis for 90 days. An equal number of control rats were sham-exposed. Following the 90-day continuous exposure period, 15 male rats were sacrificed from each group. Two rats from each group had the left kidney perfused for electron microscopic examination. The kidneys were perfused from a height of 150 cm water with 1% glutaraldehyde in Sorensen's 0.1M phosphate buffer pH 7.2. An additional kidney was taken from a rat in each group and fixed by immersion in 2.5% glutaraldehyde and 2% paraformaldehyde in 0.1M cacodylate buffer pH 7.4. A portion of the 9 kidneys collected for electron microscopy were processed into Epon 812. Thin sections, stained with uranyl acetate and lead citrate, were examined with a JEOL 100B Transmission Electron Microscope. Microvilli height was measured on photographs of the cells of proximal tubules. This data, along with morphologic features of the cells, allows the proximal convoluted tubules (PCT) to be identified as being S1, S2, or S3 segment PCT.

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Ultrastructure of rat alveolar macrophages activated in situ by poly:IC

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100128158 ◽

1987 ◽

Vol 45 ◽

pp. 768-769

Author(s):

A. M. Klinkner ◽

R. A. Weiss ◽

A. Kelley ◽

P. J. Bugelski

Keyword(s):

Venous Blood ◽

Intratracheal Instillation ◽

Buffy Coat ◽

Fischer 344 Rats ◽

Blood Monocytes ◽

Fischer 344 ◽

Polyinosinic:Polycytidylic Acid ◽

Macrophage Activator ◽

Endogenous Peroxidase

Polyinosinic:polycytidylic acid is an inducer of interferon and a macrophage activator. We have found that intratracheal instillation of polyI:C (IT-pI:C) activates rat bronchoalveolar lavage cells (BAL) for a variety of functions. Examination of Giemsa stained, cytocentrifuge preparations showed that IT-pI:C induced a population of BAL not seen in resident BAL. The morphology of these cells suggested that they might be derived from blood monocytes. To test this hypothesis we have examined several populations of macrophages that had been stained for endogenous peroxidase activity as a marker of cells derived from the monocyte-macrophage lineage.Macrophages were obtained from Fischer 344 rats. Peritoneal exudate cells (PEC) were collected by lavage 4 days after i.p. injection of 20 ml 3% thioglycolate. Buffy coat monocytes were separated from venous blood from naive rats.

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