GOLGI FRACTIONS PREPARED FROM RAT LIVER HOMOGENATES : I. Isolation Procedure and Morphological Characterization

In devising a new procedure for the isolation of Golgi fractions from rat liver homogenates, we have taken advantage of the overloading with very low density lipoprotein (VLDL) particles that occurs in the Golgi elements of hepatocytes ~90 min after ethanol is administered (0.6 g/100 g body weight) by stomach tube to the animals. The VLDLs act as morphological markers as well as density modifiers of these elements. The starting preparation is a total microsomal fraction prepared from liver homogenized (1:5) in 0.25 M sucrose. This fraction is resuspended in 1.15 M sucrose and loaded at the bottom of a discontinuous sucrose density gradient. Centrifugation at ~13 x 10⁶ g·min yields by flotation three Golgi fractions of density >1.041 and <1.173. The light and intermediate fractions consist essentially of VLDL-loaded Golgi vacuoles and cisternae. Nearly empty, often collapsed, Golgi cisternae are the main component of the heavy fraction. A procedure which subjects the Golgi fractions to hypotonic shock and shearing in a French press at pH 8.5 allows the extraction of the content of the Golgi elements and the subsequent isolation of their membranes by differential centrifugation.     

Effects of Estrogen on Glucose Uptake by Rat Muscle

The isolated rat diaphragm was used to study the effects of 17β-estradiol on basal and insulin-mediated glucose uptake. Rats were injected with estradiol for 2 wk in daily doses of 10 μg/100 g of body weight and were compared to untreated control animals. Estrogen treatment resulted in a 16% decrease in basal glucose uptake by diaphragm muscle as compared to controls. In contrast, in the presence of insulin, glucose uptake by muscle increased 103% above basal in estradiol-treated animals as compared to a 38% rise in the control group. The absolute rate of glucose uptake induced by insulin in the estradiol treated animals (5.8 mg/g/hr) was 22% higher than in controls. These findings were not accompanied by changes in weight gain, plasma glucose and plasma immunoreactive insulin concentrations in the treated animals. In vitro incubation of diaphragm muscle with estradiol did not have an effect on basal or insulin-mediated glucose uptake.     

Possibility of directed changes in the surface activity of rat pulmonary surfactants by means of exposure to antibodies specific to them]

The experiments were performed on Wistar rats with weight of 150-200 g. Antibodies were prepared by immunization of rabbits with pure surfactants of rat lungs and were intravenously injected into rats three times within 3 days intervals. These antibodies were shown to influence the superficial activity of lung surfactants and the alveolar lung cells activity. The low doses of antibodies (0.06 micrograms of protein per 100 g of body mass) stimulated the superficial activity of lung surfactants, while higher doses (3 mg of protein per 100 g of body mass) inhibited it.     

High-performance size-exclusion chromatographic analysis of dextran–methylprednisolone hemisuccinate in rat plasma

A size exclusion chromatographic method is presented for the measurement of the concentrations of a macromolecular prodrug of methylprednisolone (MP), dextran–methylprednisolone succinate (DEX–MPS), in rat plasma. After precipitation of the plasma (100 μl) proteins with perchloric acid, the samples are injected into a size exclusion column with a mobile phase of water:acetonitrile:glacial acetic acid (75:25:0.2) and a flow-rate of 1 ml/min. The DEX–MPS conjugate, detected at 250 nm, elutes at a retention time of 6.5 min, free of endogenous peaks. Excellent linear relationships (r²=0.997) were found between the detector response and the concentrations of DEX–MPS in the range of 2–100 μg/ml (MP equivalent), with intra- and inter-run C.V.s of <6% and error values of <5%. The application of the assay was also demonstrated by measurement of the plasma concentrations of DEX–MPS after single 5 or 10 mg/kg doses of the conjugate administered intravenously to rats.     

LYTIC ACTIVITIES IN RENAL PROTEIN ABSORPTION DROPLETS : An Electron Microscopical Cytochemical Study

The digestive cycle following reabsorption of hemoglobin by cells of the proximal convoluted tubules in mouse kidney and the uptake of ferritin by glomerular mesangial cells in the kidney of normal and nephrotic rats were investigated by electron microscopical histochemical procedures. Mouse kidneys, sampled at closely spaced time points between 1 to 48 hours after intraperitoneal injection of hemoglobin, and rat (normal and nephrotic) kidneys, sampled at 30 minutes, 2 hours, and 48 hours after intravenous injection of ferritin, were fixed in glutaraldehyde, cut at 50 µ on a freezing microtome, incubated for acid phosphatase and thiolacetate-esterase, and postfixed in OsO₄. Satisfactory preservation of fine structure permitted the localization of the enzymatic reaction products on cell structures involved in uptake and digestion of exogenous proteins. The latter were identified either by their density (hemoglobin) or their molecular structure (ferritin). It was found that lysosomal enzymic activities and incorporated exogenous proteins occur together in the same membrane-bounded structures. In the cells of the proximal convolution, lytic activities become demonstrable within 1 hour after hemoglobin injection, appear first in apical vacuoles filled with hemoglobin, and persist in fully formed protein absorption droplets. At the end of the lytic cycle (~48 hours post injection), the cells have an increased population of polymorphic bodies which exhibit lytic activities. In smaller numbers, identical bodies occur in controls. It is concluded that they represent remnants of previous digestive events. The means by which the resorptive vacuoles acquire hydrolytic activities remain unknown. Fusion of newly formed vacuoles with residual bodies was not seen, and hemoglobin incorporation into such bodies was only occasionally encountered. Acid phosphatase activity was found sometimes in the Golgi complex, but enzyme transport from the complex to the resorbing vacuoles could not be established. Autolytic vacuoles containing mitochondria or mitochondrial remnants were frequently found during the early stages of hemoglobin resorption, but no definite conclusions about the mechanism involved in the segregation of endogenous material were obtained. In nephrotic rats ferritin was segregated in membrane-bounded bodies mainly in the mesangial cells and to a lesser extent in epithelial and endothelial cells. Most of these sites were marked by the reaction products of acid phosphatase and organophosphorus-resistant esterase and therefore identified as lysosomes connected with the digestion of incorporated exogenous proteins.     

Distinction between binding and endocytosis of human asialo-transferrin by the rat liver

The ability of the rat liver to bind and endocytose human asialo-transferrin was investigated in vivo. Asialo-transferrin was separated from incompletely desialylated transferrin and neuraminidase by chromatography before being labelled with ¹²⁵I. Plasma radioactivity curves and hepatic radioactivity contents measured over a 1270-fold dose range led to the following observation. At the lowest dose (0.4μg/100g body wt.), the distribution of asialo-transferrin between plasma and liver resembled a reversible reaction reaching equilibrium in approx. 20min. After 35min, 93% of the dose was recovered with the plasma and liver as protein-bound radioactivity. Most of the asialo-transferrin associated with the liver could be displaced by asialo-orosomucoid, indicating that binding of asialo-transferrin to the galactose-specific lectin on the plasma membrane of hepatocytes was not followed by a signal for endocytosis. A range of doses, up to an average of 509.2μg of asialo-transferrin per 100g body wt., resulted in progressive increments in asialo-transferrin catabolism, as evidenced by lower dose recoveries and increased concentrations of non-protein-associated radioactivity in the liver and plasma volume. These observations indicate that binding and endocytosis of human asialo-transferrin by the rat hepatocyte are distinct phenomena. Individual asialo-transferrin molecules, although readily bound by the hepatic lectin, lack either the quantity or spacing of terminal galactose residues necessary for triggering endocytosis. Although endocytosis is induced by several asialo-transferrin molecules acting synergistically, preliminary experiments with asialo-glycopeptides and other substances have so far failed to provide further insight into the chemical basis of the signal for endocytosis.     

Induction of pinocytosis in rat hepatocytes by partial hepatectomy

Rat hepatocytes, normally not highly pinocytic cells, becomes so after partial hepatectomy when about two-thirds of the liver is removed. Droplets, up to 20 mum in diameter, develop, initially by addition to smaller pinocytic structures and later by fusion with lysosomes. The droplets contain a material with an electron microscope periodicity characteristic of fibrin; they are periodic acid Schiff-positive as is plasma. It is therefore reasonable to consider plasma glycoproteins to be major components of the droplets. The droplets are at all times membrane delimited, an observation possible only after perfusion fixation. The droplets are positive for three lysosomal hydrolases identified cytochemically: acid phosphatase, N-acetyl-beta-glucosaminidase, and beta-glucuronidase. From light and electron microscopy it is evident that these activities are acquired by fusion with lysosomes, mostly autophagic vacuoles and residual bodies both of which become very numerous after partial hepatectomy. Pinocytic structures are seen relatively infrequently in the hepatocytes of normal rats but a great many are present after partial hepatectomy. They are most easily observed if horseradish peroxidase (HRP) is intravenously injected before sacrifice and sections are incubated for HRP cytochemistry. The low dose of HRP employed (10 mg/100 g body weight) does not induce pinocytosis in controls, either untreated rats or rats subjected to laparotomy, including palpation of the liver. However, in partially hepatectomized rats even a much smaller dose of intravenous HRP (3.3 mg/100 g) visualizes the pinocytic structures in hepatocytes (coated vesicles, channels, cuplike bodies, and droplets). Kupffer cells pinocytose much HRP in both control and partially hepatectomized rats.     

Central cardiovascular and thermal effects of prostacyclin in rats

Prostacyclin (PGI₂) induced a dose-dependent decrease in blood pressure with slight increases in heart rate and body temperature, when administered at the doses of 0.1–100 μg into the lateral cerebral ventricle (i.c.v.) of the urethane-anaesthetised rat. When the same doses were administered intravenously, both the blood pressure and heart rate decreased. Central pretreatment with sodium meclofenamate (1 mg/rat i.c.v.) antagonised the central hypotensive effect of PGI₂ but i.c.v. pretreatment of the rats with indomethacin (1 mg/rat) failed to affect the PGO₂-induced hypotension. Central pretreatment with two histamine H₂-receptor antagonists, cimetidine (500 μg/rat i.c.v.) or metiamide (488 μg/rat i.c.v.), antagonised the blood pressure lowering effect of 0.1 μg dose of PGI₂ but failed to affect the hypotension induced by higher PGI₂ doses. Therefore the main central hypotensive effect of PGI₂ seems not to be associated with the stimulation of histamine H₂ -receptors in the brain.The hypotensive effect of i.c.v. administered PGI₂ appears to be due to an action upon the central nervous system rather than to a leakage into the peripheral circulation. This assumption is supported by the fact that sodium meclofenamate i.c.v. antagonished the effect of PGI₂. In addition, the chronotropic response to i.c.v. PGI₂ was opposite to that induced by intravenous administration. The results also suggest that there may be differences in the mode of action between sodium meclofenamate and indomethacin.     

Glucose and Fructose Have Sugar-Specific Effects in Both Liver and Skeletal Muscle In Vivo: A Role for Liver Fructokinase

We examined glucose and fructose effects on serine phosphorylation levels of a range of proteins in rat liver and muscle cells. For this, healthy adult rats were subjected to either oral glucose or fructose loads. A mini-array system was utilized to determine serine phosphorylation levels of liver and skeletal muscle proteins. A glucose oral load of 125 mg/100 g body weight (G 1/2) did not induce changes in phosphorylated serines of the proteins studied. Loading with 250 mg/100 g body weight of fructose (Fr), which induced similar glycemia levels as G 1/2, significantly increased serine phosphorylation of liver cyclin D3, PI3 kinase/p85, ERK-2, PTP2 and clusterin. The G 1/2 increased serine levels of the skeletal muscle proteins cyclin H, Cdk2, IRAK, total PKC, PTP1B, c-Raf 1, Ras and the β-subunit of the insulin receptor. The Fr induced a significant increase only in muscle serine phosphorylation of PI3 kinase/p85. The incubation of isolated rat hepatocytes with 10 mM glucose for 5 min significantly increased serine phosphorylation of 31 proteins. In contrast, incubation with 10 mM fructose produced less intense effects. Incubation with 10 mM glucose plus 75 µM fructose counteracted the effects of the incubation with glucose alone, except those on Raf-1 and Ras. Less marked effects were detected in cultured muscle cells incubated with 10 mM glucose or 10 mM glucose plus 75 µM fructose. Our results suggest that glucose and fructose act as specific functional modulators through a general mechanism that involves liver-generated signals, like micromolar fructosemia, which would inform peripheral tissues of the presence of either glucose- or fructose-derived metabolites.     

Toxicity and Mutagenicity of Hexavalent Chromium on Salmonella typhimurium

Four hexavalent and two trivalent chromium compounds were tested for toxicity and mutagenicity by means of the Salmonella typhimurium/mammalian-microsome test. All hexavalent compounds yielded a complete inhibition of bacterial growth at doses of 400 to 800 μg/plate, a significant increase of his⁺ revertant colonies at doses ranging from 10 to 200 μg, and no effect at doses of less than 10 μg. The distinctive sensitivity of the four Salmonella strains tested (TA1535, TA1537, TA98, and TA100) suggested that hexavalent chromium directly interacts with bacterial deoxyribonucleic acid by causing both frameshift mutations and basepair substitutions. The latter mutations, which are prevalent, are amplified by an error-prone recombinational repair of the damaged deoxyribonucleic acid. On the average, 1 μmol of hexavalent chromium yielded approximately 500 revertants of the TA100 strain, irrespective of the compound tested (sodium dichromate, calcium chromate, potassium chromate, or chromic acid). The mutagenic potency of the hexavalent metal was not enhanced by adding the microsomal fraction of rat hepatocytes, induced either with sodium barbital or with Aroclor 1254. The two trivalent compounds (chromium potassium sulfate and chromic chloride), with or without the microsomal fraction, were neither toxic nor mutagenic for the bacterial tester strains.     

Hexylresorcinol Induces Chromosome Aberrations in Mouse Peripheral Blood Cells

Hexylresorcinol has been demonstrated to induce chromosome aberrations in eukaryotic cells at doses of 0.5, 0.05, and 0.005 mg/g body weight. The metabolic transformation of hexylresorcinol in mice decreases its genotoxic effect. The mutagenic effect is retained for three days only after the administration of the highest dose of hexylresorcinol (0.5 mg/g); during the first two days, lower doses are also genotoxic. Therefore, hexylresorcinol doses lower than 0.5 mg/g body weight are metabolized within two days to the extent precluding the expression of the cytotoxic effect. After a single administration to mice, exogenous hexylresorcinol is transformed at a rate of 0.0025–0.025 mg/day.__________Translated from Genetika, Vol. 41, No. 8, 2005, pp. 1045–1048.Original Russian Text Copyright © 2005 by Margulis, Ozhiganova, Bushmanova, Kolpakov, Il’inskaya.     

Assessment of the genotoxicity of imidacloprid and metalaxyl in cultured human lymphocytes and rat bone-marrow

Imidacloprid and metalaxyl are two pesticides that are widely used in agriculture, either separately, or in combination. These agents were studied for their possible genotoxic effects with respect to the following cytogenetic end-points: (1) in vitro micronucleus (MN) formation and sister-chromatid exchange (SCE) induction in human lymphocytes and (2) in vivo micronucleus induction in polychromatic erythrocytes (PCEs) of the rat bone-marrow. The results of the MN analysis indicate that MN frequencies after treatment with both pesticides, separately or as a mixture, do not significantly differ from those in the controls except after treatment with metalaxyl alone at 50 μg/ml (p < 0.05). The results of the SCE analysis show that SCE frequencies after treatment with imidacloprid do not differ significantly from those in the controls. A statistically significant increase (p < 0.05) in SCE frequency resulted from treatments with metalaxyl at 5, 10 and 100 μg/ml and with the combination of imidacloprid and metalaxyl at 100 and 200 μg/ml. Finally, the in vivo micronucleus assay with rat bone-marrow polychromatic erythrocytes showed a statistically significant effect upon separate treatments with imidacloprid and metalaxyl at doses of 300 mg/kg body weight (b.w.) (p < 0.01) or upon combined treatment with 200 mg/Kg b.w. (p < 0.001) and 400 mg/kg b.w. (p < 0.05).     

Prostaglandin hyperalgesia, V: A peripheral analgesic receptor for opiates

Prostaglandin E₂ injected in the rat paw causes hyperalgesia which is antagonized by local injections of opiate and opiate antagonists. In the present investigation in rats it i shown at naloxone has an analgesic effect at doses as low as 2 μg/site, injected into the rat hind paw. At a dose that has no analgesic effect (1 μg/site) naloxone antagonized the analgesia produced by either local or systematic administration of morphine. Local administration of levorphanol (50 μg/site) caused a 50% reduction in the intensity of the hyperalgesia induced by prostaglandin E₂. A dose four times greater of its isomer, dextrorphan, had little analgesic effect. The present results support the suggestion that this peripheral analgesia is the result of an action of opiates in receptors located at the nociceptors.     

The control of liver regeneration by parathyroid hormone and Calcium

Following partial hepatectomy in rats, there were two bursts of hepatocyte DNA-synthetic and mitotic activity which were produced by two subpopulations having different rates of (nearly synchronous) proliferative development. Only about 50% of the cells in both subpopulations could initiate DNA synthesis and enter mitosis when exposed to the hypocalcemic conditions in the parathyroprivic rat for 24 hours before partial hepatectomy. The proliferatively incompetent hepatocytes in these hypocalcemic rats could be induced to initiate their DNA synthetic and mitotic activity by an intraperitoneal injection of the calcium-mobilizing parathyroid hormone (50 USP units/100 g) as late as 12 hours after partial hepatectomy. Single intraperitoneal injections of calcium (0.25 mg/100 g) could also restore the proliferative competence of these hepatocytes, but only when injected at specific periods following partial hepatectomy. The injection of calcium 12 to 15 hours after partial hepatectomy induced hepatocytes in the first subpopulation to finish their development and enter mitosis, but did not affect the second, more slowly developing, subpopulation. Calcium had to be injected 25 hours after partial hepatectomy to stimulate proliferation in this second subpopulation. These data suggest that the hepatocytes which became proliferatively incompetent by prolonged exposure to a hypocalcemic environment are proliferatively activated by partial hepatectomy, but their proliferative development stops at a calcium-dependent stage near the end of the pre-replicative phase of development.     

The control of liver regeneration by parathyroid hormone and calcium.

Following partial hepatectomy in rats, there were two bursts of hepatocyte DNA-synthetic and mitotic activity which were produced by two subpopulations having different rates of (nearly synchronous) proliferative development. Only about 50% of the cells in both subpopulations could initiate DNA synthesis and enter mitosis when exposed to the hypocalcemic conditions in the parathyroprivic rat for 24 hours before partial hepatectomy. The proliferatively incompetent hepatocytes in these hypocalcemic rats could be induced to initiate their DNA synthetic and mitotic activity by an intraperitoneal injection of the calcium-mobilizing parathyroid hormone (50 USP units/100 g) as late as 12 hours after partial hepatectomy. Single intraperitoneal injections of calcium (0.25 mg/100 g) could also restore the proliferative competence of these hepatocytes, but only when injected at specific periods following partial hepatectomy. The injection of calcium 12 to 15 hours after partial hepatectomy induced hepatocytes in the first subpopulation to finish their development and enter mitosis, but did not affect the second, more slowly developing, subpopulation. Calcium had to be injected 25 hours after partial hepatectomy to stimulate proliferation in this second subpopulation. These data suggest that the hepatocytes which became proliferatively incompetent by prolonged exposure to a hypocalcemic environment are proliferatively activated by partial hepatectomy, but their proliferative development stops at a calcium-dependent stage near the end of the pre-replicative phase of development.     

Effects of Different Pulmonary Vasodilators on Arterial Saturation in a Model of Pulmonary Hypertension

Background

Approved therapies for pulmonary arterial hypertension can induce oxygen desaturation when administered to patients with secondary forms of pulmonary hypertension (PH), probably due to an increase in ventilation/perfusion mismatch. Thus, so far these treatments have largely failed in secondary forms of PH.

Methods

We established an animal model of heterogeneous lung ventilation to evaluate the desaturation potential of mechanistically distinct vasoactive drugs launched or currently in clinical development for the treatment of PH. Single-lung ventilation was induced in five groups (N = 6) of anesthetized minipigs (7 weeks, 4 to 5 kg BW), and their hemodynamic parameters were monitored before and after intravenous injection of control (vehicle only), endothelin antagonist (bosentan; 0.3, 1, 3, 10 mg/kg), phosphodiesterase type 5 inhibitor (sildenafil; 3, 10, 30, 100 µg/kg), and soluble guanylate cyclase stimulators (BAY 41–8543 and riociguat; 1, 3, 10, 30 µg/kg). Cumulative doses were administered before successive unilateral ventilation cycles. The doses were chosen to achieve equal effect on blood pressure by the different pharmacologic principles.

Results

Single-lung ventilation resulted in transient increases in mean pulmonary artery pressure (mPAP) and desaturation. In contrast to control, all drugs dose-dependently decreased hypoxic mPAP (a positive treatment effect) and increased area under the arterial hemoglobin saturation curve (unwanted desaturation effect). Riociguat and bosentan reduced hypoxic mPAP to the greatest extent, while the soluble guanylate cyclase stimulators riociguat and BAY 41–8543 lowered arterial oxygen saturation of hemoglobin the least.

Conclusions

Future investigations will be required to confirm these findings in clinical settings.     

Effect of beta-N-oxalylamino-l-alanine on cerebellar cGMP level in vivo

Beta-N-oxalylamino-l-alanine (BOAA), a non-protein amino acid present in the seeds of Lathyrus Sativus (LS), is one of several neuroactive glutamate analogs reported to stimulate excitatory receptors and, in high concentrations, cause neuronal degeneration. In the present study, the in vivo acute effects of synthetic BOAA and LS seed extract were investigated on rat cerebellar cyclic GMP following intraperitoneal (10–100 mg/kg) or oral (100 mg/kg) administration of subconvulsive doses of toxin. Furthermore, the BOAA content in LS seeds and in the cerebellum of injected rats was determined by high performance liquid chromatograph analysis. A dose- and time-dependent increase of cerebellar cyclic guanosine monophosphate (cGMP) level was observed after intraperitoneal administration of synthetic BOAA or LS extract. The neurotoxin evoked a maximum stimulation 90 min after injection within the dose range of 50–75 mg/kg, elevating cGMP from basal levels of 5.3±0.5 pmol/mg protein to 15±1.3 pmol/mg protein. Similarly, the oral intake of LS-extracted neurotoxin resulted in the elevation of cGMP content. Kynurenic acid (300 mg/kg i.p.), a non specific excitatory amino acid antagonist, was effective in blocking LS BOAA-elicited cGMP enhancement. The data suggest that in the cerebellum acute administration of low concentrations of BOAA exert in vivo activation of glutamate receptors involved in the regulation of cGMP level.     

Protection against salicylate-induced hepatic injury by zinc. A histochemical and biochemical study

Summary Female Wistar rats received an oral dose of 700 mg salicylic acid/kg body wt., given as sodium salicylate. Some of the salicylate-treated rats received two subcutaneous injections of 100 mol kg^–1 ZnCl₂ (24 h before and simultaneously with the salicylate administration). Other animals were given one subcutaneous injection of 100 mol kg^–1 ZnCl₂ simultaneously with the salicylate treatment. Control rats were similarly injected with ZnCl₂. Twenty four hours after salicylate treatment, serum and livers were taken for histochemical and biochemical analysis. The most remarkable effects of the treatment were enrichment of lipid droplets and iron and a reduction of glycogen, particularly in the periportal hepatocytes. The effects of salicylate were partially prevented by two ZnCl₂ injections. The protective effects of ZnCl₂ may be due to lower iron uptake into hepatocytes and by the induction of zinc metallothionein, which can serve as a scavenger for oxygen radicals.     

Reproductive toxicologic evaluations of Bulbine natalensis Baker stem extract in albino rats

The effects of oral administration of aqueous extract of Bulbine natalensis Baker stem at daily doses of 25, 50, and 100 mg/kg body weight on the reproductive function of Wistar rats were evaluated. The indices of mating and fertility success as well as quantal frequency increased after 7 days of treatment in all the dose groups except the 100 mg/kg body weight group. The number of litters was not statistically different (P > 0.05) from the control. Whereas the absolute weights of the epididymis, seminal vesicle, and prostate were not affected, that of the testes was significantly increased. The epididymal sperm count, motility, morphology, and viscosity were not different from the control after 7 days of treatment. The male rat serum testosterone, progesterone, luteinizing hormone, and follicle-stimulating hormone significantly increased in the 25 and 50 mg/kg body weight groups, whereas the estradiol concentration decreased significantly at all the doses. The extract dose of 100 mg/kg body weight decreased the serum testosterone and progesterone levels in male rats. The prolactin concentration was not affected by all the doses. All the indices of reproduction, maternal, embryo/fetotoxic, teratogenic, and reproductive hormones in the female rats were not statistically different from that of their control except the resorption index, which increased at the dose of 100 mg/kg body weight of the extract. Histologic examination of the cross section of rat testes that received the extract at all the doses investigated revealed well-preserved seminiferous tubules with normal amount of stroma, normal population of spermatogenic and supporting cells, as well as normal spermatocytes within the lumen. The results revealed that the aqueous extract of Bulbine natalensis stem at doses of 25 and 50 mg/kg body weight enhanced the success rate of mating and fertility due to increased libido as well as the levels of reproductive hormones in male rats. The absence of alterations in the reproductive parameters of female rats at doses of 25 and 50 mg/kg body weight of Bulbine natalensis stem extract suggest that the extract is “safe” for use at these doses by females during the organogenic period of pregnancy, whereas the extract dose of 100 mg/kg body weight portends a negative effect on some reproductive functions of male and female rats.